code: def get_distribution_names(self):
          
          result = set()
          for root, dirs, files in os.walk(self.base_dir):
              for fn in files:
                  if self.should_include(fn, root):
                      fn = os.path.join(root, fn)
                      url = urlunparse(('file', '',
                                        pathname2url(os.path.abspath(fn)),
                                        '', '', ''))
                      info = self.convert_url_to_download_info(url, None)
                      if info:
                          result.add(info['name'])
              if not self.recursive:
                  break
          return result
docs: Return all the distribution names known to this locator.