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).

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}