ipywidgets -- fix according by adding appropriate styles

Author: williamstein

src/packages/frontend/_jupyter.sass

@@ -3,6 +3,9 @@
  *  License: AGPLv3 s.t. "Commons Clause" – see LICENSE.md for details
  */
 
+// I just noticed there is another version of this file in jupyter/_jupyter.sass
+// They need to be carefully merged into one!  But not today.
+
 .smc-jupyter-nbviewer-content
   border: 1px solid lightgray
 
@@ -114,6 +117,12 @@
   .katex
     padding: 0 2.5px
 
+// this seems to be missing from jupyter widgets, but is used to implement the according
+//   https://ipywidgets.readthedocs.io/en/latest/examples/Widget%20List.html#accordion
+// I.e., without this css rule, accordian is just broken.
+.lm-Widget.lm-mod-hidden
+  display: none !important
+
 .cc-jupyter-buttonbar-dropdown
   .ant-dropdown-menu-item
     color: $COL_GRAY_D !important

src/packages/frontend/jupyter/_jupyter.sass

@@ -3,6 +3,9 @@
  *  License: AGPLv3 s.t. "Commons Clause" – see LICENSE.md for details
  */
 
+// I just noticed there is another version of this file in ../_jupyter.sass
+// They need to be carefully merged into one!  But not today.
+
 .cocalc-jupyter-rendered
   img
     max-width: 100%