docs: def parse_doc_tree(self, doctree, pypackages):
          """Parse the given documentation tree.
  
          :param str doctree: The absolute path to the documentation tree which is to be parsed.
          :param set pypackages: A set of all Python packages found in the pytree.
          :rtype: dict
          :returns: A dict where each key is the path of an expected Python module and its value is
              the parsed rst module name (relative to the documentation tree).
          """
          parsed_doctree = {}
          for filename in os.listdir(doctree):
              if self._ignore_docfile(filename):
                  continue
  
              expected_pyfile = self.build_pyfile_path_from_docname(filename)
              parsed_doctree[expected_pyfile] = filename
  
          pypackages = {name + '.py' for name in pypackages}
          return {elem: parsed_doctree[elem] for elem in parsed_doctree if elem not in pypackages}