diff --git a/doc/source/ystatic/dark_theme.css b/doc/source/ystatic/dark_theme.css
deleted file mode 100644
index 239aa462b..000000000
--- a/doc/source/ystatic/dark_theme.css
+++ /dev/null
@@ -1,720 +0,0 @@
-/*
- * flasky.css_t
- * ~~~~~~~~~~~~
- *
- * :copyright: Copyright 2010 by Armin Ronacher. Modifications by Kenneth Reitz.
- * :license: Flask Design License, see LICENSE for details.
- */
-
-
-
-
-
- @import url("basic.css");
-
- /* -- page layout ----------------------------------------------------------- */
- 
- body {
-     font: 400 16px Lato, 'Helvetica Neue', Helvetica, Arial, sans-serif;
-     /*font-family: 'goudy old style', 'minion pro', 'bell mt', Georgia, 'Hiragino Mincho Pro';
-     font-size: 17px; */
-     line-height: normal;
-     background-color: #333;
-     color: #333;
-     margin: 0;
-     padding: 0;
-     text-shadow: 0 1px 3px rgba(0,0,0,0.5);
- }
- 
- strong {
-     font-weight: bold;
- }
- 
- div.document {
-     width: 1024px;
-     margin: 30px auto 0 auto;
- }
- 
- div.documentwrapper {
-     float: left;
-     width: 100%;
- }
- 
- div.bodywrapper {
-     margin: 0 0 0 220px;
- }
- 
- div.sphinxsidebar {
-     width: 220px;
- }
- 
- hr {
-     border: 1px solid #B1B4B6;
- }
- 
- div.body {
-     background-color: #444;
-     border-radius: 5px;
-     color: #ddd;
-     padding: 15px 30px 15px 30px;
-     box-shadow: 0 3px 10px rgba(0,0,0,0.3);
- }
- 
- img.floatingflask {
-     padding: 0 0 10px 10px;
-     float: right;
- }
- 
- div.footer {
-     width: 1024px;
-     margin: 20px auto 30px auto;
-     font-size: 14px;
-     color: #888;
-     text-align: right;
- }
- 
- div.footer a {
-     color: #888;
- }
- 
- div.related {
-     display: none;
- }
- 
- div.sphinxsidebar a {
-     color: #FFCC00;
-     text-decoration: none;
-     border-bottom: none;
- }
- div.sphinxsidebar a:hover {
-     color: #ff9900;
- }
- 
- div.sphinxsidebar a:hover,
- div.sphinxsidebar a:visited,
- div.sphinxsidebar a:focus {
-     border-bottom: none;
- }
- 
- div.sphinxsidebar {
-     margin: 0;
-     position: fixed;
-     overflow: auto;
-     height: auto;
-     font-size: 14px;
-     line-height: 1.5;
- }
- 
- div.sphinxsidebarwrapper {
-     padding: 18px 0 18px 10px;
- }
- 
- div.sphinxsidebarwrapper p.logo {
-     padding: 0;
-     margin: -10px 0 0 -20px;
-     text-align: center;
- }
- 
- div.sphinxsidebar h3,
- div.sphinxsidebar h4 {
-     /*font-family: 'Garamond', 'Georgia', serif;*/
-     font-family: Lato, 'Helvetica Neue', Helvetica, Arial, sans-serif;
-     color: #ddd;
-     font-size: 20px;
-     font-weight: normal;
-     padding: 0;
-     /*border-bottom: 1px solid #fff;*/
- 
-     background-color: #444;
-     border-radius: 5px 0 0 0px;
-     padding-left: 5px;
-     border: 1px solid #444;
-     margin-top: 10px;
-     box-shadow: 0 3px 10px rgba(0,0,0,0.3);
-     margin-left: -10px;
-     /* Needed, if siebar is not sticky. Otherwise shadows moves over body element*/
-     clip-path: inset(-10px -0px -10px -10px);
- }
- 
- div.sphinxsidebar h4 {
-     font-size: 20px;
- }
- 
- div.sphinxsidebar h3 a {
-     color: #ddd;
- }
- 
- div.sphinxsidebar p.logo a,
- div.sphinxsidebar h3 a,
- div.sphinxsidebar p.logo a:hover,
- div.sphinxsidebar h3 a:hover {
-     border: none;
- }
- 
- div.sphinxsidebar p {
-     color: #555;
-     margin: 10px 0;
- }
- 
- div.sphinxsidebar ul {
-     margin: 0;
-     padding: 0;
-     color: #ddd;
- }
- 
- div.sphinxsidebar input {
-     /*border: 1px solid #ccc;*/
-     border: 1px solid #333;
-     font-family: 'Georgia', serif;
-     font-size: 1em;
-     color: #ddd;
-     width: 170px;
-     border-radius: 5px;
-     padding: 6px 12px;
-     box-shadow: inset 0 1px 10px rgba(0,0,0,0.3), 0 1px 0 rgba(255,255,255,0.1), 0 0px 0 rgba(0,0,0,0.5);
-     background-color: #2b2b2b;
- }
- 
- div.need-tobediscussed {
-  background-color: #0a4a63 !important;
- }
- 
- /*span.needs-type {*/
-     /*border: 1px solid #444;*/
-     /*border-radius: 5px;*/
-     /*padding: 3px 5px;*/
- /*}*/
- 
- /*div.need-implementation span.needs-type {*/
-     /*!*background-color: #ffdd00 !important;*!*/
-     /*border: 1px solid #ffdd00*/
- /*}*/
- 
- div.need-status-closed span.needs-status {
-     background-color:darkgreen;
- }
- 
- div.need-status-open span.needs-status {
-     background-color:firebrick;
- }
- 
- div.need-status-tbd span.needs-status {
-     background-color:orange;
- }
- 
- div.need-technicaldebt span.needs-type {
-     background-color:red;
- }
- 
- /* need part table layout */
- tr.need_part td {
-     background-color: #555;
-     padding-left: 30px !important;
- }
- 
- /* using more space for whole page */
- div.document {
-     width: auto;
-     margin: 30px auto 0 auto;
-     max-width: 98%;
- }
- div.body {
-     min-width: 450px;
-     max-width: 100%;
- }
- 
- span.need-part a {
-     font-size: 0.75em;
- }
- span.need-part {
-     border-bottom: 1px solid #888;
- }
- 
- /* Code block design  inside needs */
- div.need pre {
-     margin: 0;
- }
- 
- /* Better need title and ID layout*/
- span.needs-id {
-     font-size: 120% !important;
-     color: #ffcc00 !important;
-     float:right
- }
- span.needs-title {
-     font-weight: bold;
-     font-size: 1.3em;
- }
- 
- div.needs_meta div.headline {
-     margin-bottom: 5px;
-     border-bottom: 1px solid #555;
- }
- div.needs_meta.line-block{
-     margin: 0;
- }
- 
- /* Need headline color design*/
- div.needs_meta div.headline {
-     margin: -5px -10px 5px -10px;
-     border-bottom: 1px solid #555;
-     border-radius: 3px 3px 0 0;
-     padding: 5px 10px 0px 10px;
- }
- 
- div.story div.headline {
-     background-color: #39024e80;
- }
- 
- div.spec div.headline {
-     background-color: #00beff33;
- }
- 
- div.impl div.headline {
-     background-color: #ff000a33;
- }
- 
- div.test div.headline {
-     background-color: #2ed15233;
- }
- /* -- body styles ----------------------------------------------------------- */
- 
- a {
-     color: #FFCC00;
-     text-decoration: none;
- }
- 
- a:hover {
-     color: #ff9900;
-     text-decoration: none;
- }
- 
- div.body h1,
- div.body h2,
- div.body h3,
- div.body h4,
- div.body h5,
- div.body h6 {
-     font-family: Lato, 'Helvetica Neue', Helvetica, Arial, sans-serif;
-     /*font-family: 'Garamond', 'Georgia', serif;*/
-     font-weight: normal;
-     /* margin: 30px 0px 10px 0px; */
-     margin: 10px 0px 00px 0px;
-     padding: 0;
- }
- 
- div.body h1 { margin-top: 0; padding-top: 0; font-size: 240%; }
- div.body h2 { font-size: 180%; }
- div.body h3 { font-size: 150%; }
- div.body h4 { font-size: 130%; }
- div.body h5 { font-size: 100%; }
- div.body h6 { font-size: 100%; }
- 
- a.headerlink {
-     color: #ffcc00;
-     padding: 0 4px;
-     text-decoration: none;
-     text-shadow: none;
- }
- 
- a.headerlink:hover {
-     color: #ff9900;
-     background: none;
-     text-shadow: none;
- }
- 
- div.body p, div.body dd, div.body li {
-     line-height: 1.4em;
- }
- 
- div.admonition {
-     background: none;
-     margin: 20px -30px;
-     padding: 10px 30px;
- }
- 
- div.admonition tt.xref, div.admonition a tt {
-     border-bottom: 1px solid #fafafa;
- }
- 
- dd div.admonition {
-     margin-left: -60px;
-     padding-left: 60px;
- }
- 
- div.admonition p.admonition-title {
-     font-family: Lato, 'Helvetica Neue', Helvetica, Arial, sans-serif;
-     /* font-family: 'Garamond', 'Georgia', serif; */
-     /* font-weight: normal;/*
-     font-weight: bold;
-     /* font-size: 24px; */
-     font-size: 18px;
-     margin: 0 0 10px 0;
-     padding: 0;
-     line-height: 1;
- }
- 
- div.admonition p.last {
-     margin-bottom: 0;
- }
- 
- div.highlight {
-     /*background-color: white;*/
-     background-color: #444;
-     text-shadow: none;
-     color: #fff;
- }
- 
- dt:target, .highlight {
-     background: #333;
- }
- 
- div.note {
-     background-color: #555;
-     border: none;
- }
- 
- div.warning {
-     background-color: #7f1212;
-     border: none;
- }
- 
- div.seealso {
-     background-color: #ffc;
-     border: 1px solid #ff6;
- }
- 
- div.topic {
-     background-color: inherit;
-     border: none;
- }
- 
- p.admonition-title {
-     display: inline;
- }
- 
- p.admonition-title:after {
-     content: ":";
- }
- 
- pre, tt {
-     font-family: 'Consolas', 'Menlo', 'Deja Vu Sans Mono', 'Bitstream Vera Sans Mono', monospace;
-     font-size: 0.9em;
- }
- 
- img.screenshot {
- }
- 
- tt.descname, tt.descclassname {
-     font-size: 0.95em;
- }
- 
- tt.descname {
-     padding-right: 0.08em;
- }
- 
- img.screenshot {
-     -moz-box-shadow: 2px 2px 4px #eee;
-     -webkit-box-shadow: 2px 2px 4px #eee;
-     box-shadow: 2px 2px 4px #eee;
- }
- 
- table.docutils {
-     border: 1px solid #888;
-     -moz-box-shadow: 2px 2px 4px #eee;
-     /* -webkit-box-shadow: 2px 2px 4px #eee; */
-     /* box-shadow: 2px 2px 4px #eee; */
- }
- 
- table.docutils td, table.docutils th {
-     border: 1px solid #888;
-     padding: 0.25em 0.7em;
- }
- 
- table.field-list, table.footnote {
-     border: none;
-     -moz-box-shadow: none;
-     -webkit-box-shadow: none;
-     box-shadow: none;
- }
- 
- table.footnote {
-     margin: 15px 0;
-     width: 100%;
-     border: 1px solid #eee;
-     background: #fdfdfd;
-     font-size: 0.9em;
- }
- 
- table.footnote + table.footnote {
-     margin-top: -15px;
-     border-top: none;
- }
- 
- table.field-list th {
-     padding: 0 0.8em 0 0;
- }
- 
- table.field-list td {
-     padding: 0;
- }
- 
- table.footnote td.label {
-     width: 0px;
-     padding: 0.3em 0 0.3em 0.5em;
- }
- 
- table.footnote td {
-     padding: 0.3em 0.5em;
- }
- 
- dl {
-     margin: 0;
-     padding: 0;
- }
- 
- dl dd {
-     margin-left: 30px;
- }
- 
- blockquote {
-     margin: 0 0 0 30px;
-     padding: 0;
- }
- 
- ul, ol {
-     margin: 10px 0 10px 30px;
-     padding: 0;
- }
- 
- pre {
-     background: #2b2b2b;
-     padding: 7px 30px;
-     margin: 15px -30px;
-     line-height: 1.3em;
-     box-shadow: inset 0 1px 10px rgba(0,0,0,0.3),0 1px 0 rgba(255,255,255,0.1),0 -1px 0 rgba(0,0,0,0.5);
- }
- 
- dl pre, blockquote pre, li pre {
-     margin-left: -60px;
-     padding-left: 60px;
- }
- 
- dl dl pre {
-     margin-left: -90px;
-     padding-left: 90px;
- }
- 
- tt {
-     background-color: #ecf0f3;
-     color: #222;
-     /* padding: 1px 2px; */
- }
- 
- tt.xref, a tt {
-     background-color: #FBFBFB;
-     border-bottom: 1px solid white;
- }
- 
- a.reference {
-     text-decoration: none;
-     border-bottom: none;
- }
- 
- a.reference:hover {
-     border-bottom: none;
- }
- 
- a.footnote-reference {
-     text-decoration: none;
-     font-size: 0.7em;
-     vertical-align: top;
-     border-bottom: 1px dotted #004B6B;
- }
- 
- a.footnote-reference:hover {
-     border-bottom: 1px solid #6D4100;
- }
- 
- a:hover tt {
-     background: #EEE;
- }
- 
- @media screen and (max-width: 600px) {
- 
-     .github_fork {
-         display: none;
-     }
- 
-     div.sphinxsidebar {
-         display: none;
-     }
- 
-     div.document {
-        width: 100%;
- 
-     }
- 
-     div.documentwrapper {
-         margin-left: 0;
-         margin-top: 0;
-         margin-right: 0;
-         margin-bottom: 0;
-     }
- 
-     div.bodywrapper {
-         margin-top: 0;
-         margin-right: 0;
-         margin-bottom: 0;
-         margin-left: 0;
-     }
- 
-     ul {
-         margin-left: 30;
-     }
- 
-     .document {
-         width: auto;
-     }
- 
-     .footer {
-         width: auto;
-     }
- 
-     .bodywrapper {
-         margin: 0;
-     }
- 
-     .footer {
-         width: auto;
-     }
- 
-     .github {
-         display: none;
-     }
- 
- }
- 
- /* misc. */
- 
- .revsys-inline {
-     display: none!important;
- }
- 
- /* API layout */
- 
- code.descname {
-     color : #ffffff;
- }
- 
- /* Pygmets overwrites  */
- .highlight .nf { color: #ffcc00 !important; } /* function name */
- .highlight .nc { color: #ffcc00 !important; } /* class name */
- .highlight .kn { color: #918a6f !important; } /* import name */
- .highlight .bp { color: #ffffff !important; } /* self, name */
- .highlight .k { color: #918a6f !important; } /*  class, def name */
- .highlight .o { color: #ffffff !important; } /* function name */
- .highlight .nb { color: #ffffff !important; } /* super, print name */
- .highlight .go { color: #aaaaaa !important; } /* super, print name */
- 
- 
- /*
- Needed for readthedocs.io, because it adding its own css, which destroy our images.
- See https://github.com/rtfd/readthedocs.org/issues/2348
- */
- /* img {
-     width: auto !important;
- }*/
- 
- 
- div.sidebar {
-     background-color: #2b2b2b;
-     border: none;
-     margin: 0 -30px 0 0;
-     box-shadow: inset 0 1px 10px rgba(0,0,0,0.3),0 1px 0 rgba(255,255,255,0.1),0 -1px 0 rgba(0,0,0,0.5);
-     border-radius: 10px 0 0 10px;
-     padding: 10px 20px 0 20px;
-     text-align: justify;
- }
- 
- 
- div.sidebar div.topic {
-     background-color: transparent;
-     border: none;
-     margin-top: -20px;
- }
- }
- 
- div.sidebar div.topic ul {
-     margin: 5px 0 5px 15px;
- }
- 
- div.sidebar div.topic p.topic-title {
-     display: none;
- }
- 
- table.indextable tr.cap {
-     background-color: transparent !important;
- }
- 
- div.figure p.caption {
-     text-align: center
- }
- 
- table.highlighttable pre {
-     margin: 0;
- }
- 
- table.highlighttable {
-     /* margin: 0; */
-     width: 100%;
-     border-spacing: 0px;
-     margin: 0 -30px 0 -30px;
-     overflow: auto;
- }
- 
- div.highlight-python, div.highlight-jinja {
- 
- }
- 
- div.highlight-json .nt {
-     color: #ff9900;
- }
- 
- table.highlighttable td {
-  padding: 0;
- }
- 
- div.linenodiv {
-     background-color: #2b2b2b;
-     padding: 0;
- }
- 
- td.linenos pre  {
-     padding: 7px 5px;
- }
- td.code div.highlight pre {
-     width: 717px;
-     overflow: hidden;
- }
- 
- .highlight .hll {
-     background-color: #353535 !important;
- }
- 
- p.plantuml object {
-     width: 100% !important;
-     height: 100% !important;
- 
- }
- 
- .highlighted {
-     background-color: transparent;
-     color: #0e84b5;
- 
- }
- 
- /* Sidebar TOC: make the current chapter bold */
- .current.reference.internal {
-     font-weight: bold;
- }
\ No newline at end of file