def _update_focal_loss_alpha(configs, alpha):
  """Updates the alpha value for a sigmoid focal loss.

  The configs dictionary is updated in place, and hence not returned.

  Args:
    configs: Dictionary of configuration objects. See outputs from
      get_configs_from_pipeline_file() or get_configs_from_multiple_files().
    alpha: Class weight multiplier for sigmoid loss.

  Raises:
    TypeError: If the classification loss is not `weighted_sigmoid_focal`.
  """
  classification_loss = _get_classification_loss(configs["model"])
  classification_loss_type = classification_loss.WhichOneof(
      "classification_loss")
  if classification_loss_type != "weighted_sigmoid_focal":
    raise TypeError("Classification loss must be `weighted_sigmoid_focal`.")
  classification_loss.weighted_sigmoid_focal.alpha = alpha
Updates the alpha value for a sigmoid focal loss.

  The configs dictionary is updated in place, and hence not returned.

  Args:
    configs: Dictionary of configuration objects. See outputs from
      get_configs_from_pipeline_file() or get_configs_from_multiple_files().
    alpha: Class weight multiplier for sigmoid loss.

  Raises:
    TypeError: If the classification loss is not `weighted_sigmoid_focal`.
  
inference_api/src/main/object_detection/utils/config_util.py