code: def extendMarkdown(self, md, md_globals=None):
          
          if any(
                  x not in md.treeprocessors
                  for x in self.REQUIRED_EXTENSION_INTERNAL_NAMES):
              raise RuntimeError(
                  "The attr_cols markdown extension depends the following"
                  " extensions which must preceded it in the extension"
                  " list: %s" % ", ".join(self.REQUIRED_EXTENSIONS))
          processor = AttrColTreeProcessor(md, self.conf)
          md.treeprocessors.register(
              processor, 'attr_cols',
              5)
docs: Initializes markdown extension components.