Question - How can I mark icons as translatable=no ?

There are 43 strings in several .sheet files and they have not been marked as translatable but they have been in the PO files.

For example:

#: sheets/ER.sheet:11
msgid "res:/org/gnome/Dia/ER/weakentity.png"
msgstr "res:/org/gnome/Dia/ER/weakentity.png"

The current code is:

    <object name="ER - Entity" intdata="1">
      <description>Weak entity</description>
      <icon>res:/org/gnome/Dia/ER/weakentity.png</icon>
    </object>

I marked the icon tags as translatable="no", but it had no effect on them.

    <object name="ER - Entity" intdata="1">
      <description>Weak entity</description>
      <icon translatable="no">res:/org/gnome/Dia/ER/weakentity.png</icon>
    </object>

I also added this line to /po/its/sheet.its (https://gitlab.gnome.org/GNOME/dia/blob/master/po/its/sheet.its) file but again had no effect.

<its:translateRule selector="/sheet/contents/object/icon" translate="no"/>