code: def add_fixed(self, path, langs, category=SourceRootCategories.UNKNOWN):
      
      if '*' in path:
        raise self.InvalidPath(path, 'fixed path cannot contain the * character')
      fixed_path = os.path.join('^', path) if path else '^'
      self._do_add_pattern(fixed_path, tuple(langs), category)
docs: Add a fixed source root to the trie.