Updates absl logging levels to the current verbosity.

def _update_logging_levels(self):
    """Updates absl logging levels to the current verbosity."""
    if not _absl_logger:
      return

    if self._value <= converter.ABSL_DEBUG:
      standard_verbosity = converter.absl_to_standard(self._value)
    else:
      # --verbosity is set to higher than 1 for vlog.
      standard_verbosity = logging.DEBUG - (self._value - 1)

    # Also update root level when absl_handler is used.
    if _absl_handler in logging.root.handlers:
      logging.root.setLevel(standard_verbosity)