Merge pull request #782 from adamtheturtle/rm-unnecessary-isinstance-2

Remove unnecessary assert isinstance

src/sphinx_substitution_extensions/__init__.py

@@ -138,7 +138,6 @@ def process_link(
         Override parent method to replace placeholders with given variables.
         """
         document = self.inliner.document
-        assert isinstance(document, docutils.nodes.document)
         for name, value in document.substitution_defs.items():
             replacement = value.astext()
             title = title.replace(f"|{name}|", replacement)