code: def _package_top_dir(self):
          
          r = [self.package_dir]
          for l in self._pip_locations:
              if l is not None:
                  r.append(l)
          for l in self._pkg_resources_locations:
              if l is not None:
                  r.append(l)
          return sorted(list(set(r)))
docs: Find one or more directories that we think may be the top-level
          directory of the package; return a list of their absolute paths.
  
          :return: list of possible package top-level directories (absolute paths)
          :rtype: list