code: def _read_yaml_file(self, yaml_file):
          # type: (CliContext, pathlib.Path) -> None
          
          with yaml_file.open('r') as f:
              if self.config is None:
                  self.config = ruamel.yaml.load(
                      f, Loader=ruamel.yaml.RoundTripLoader)
              else:
                  self.config = blobxfer.util.merge_dict(
                      ruamel.yaml.load(f, Loader=ruamel.yaml.RoundTripLoader),
                      self.config)
docs: Read a yaml file into self.config
          :param CliContext self: this
          :param pathlib.Path yaml_file: yaml file to load