code: def _parse_config_file_impl(filename):
      
      try:
          doc = yaml.load(file(filename).read())
          
          project_id = doc["credentials"]["project_id"]
          access_token = doc["credentials"]["access_token"]
          api_domain = doc["credentials"]["api_domain"]
          
          return project_id, access_token, api_domain
      except:
          return None, None, None
docs: Format for the file is:
      
           credentials:
               project_id: ...
               access_token: ...
               api_domain: ...
      
      :param filename: The filename to parse
      :return: A tuple with:
                  - project_id
                  - access_token
                  - api_domain