Setup gin configuration.

def _setup_gin():
  """Setup gin configuration."""
  # Imports for configurables
  # pylint: disable=g-import-not-at-top,unused-import,g-bad-import-order,reimported,unused-variable
  from tensor2tensor.trax import models as _trax_models
  from tensor2tensor.trax import optimizers as _trax_opt
  # pylint: disable=g-import-not-at-top,unused-import,g-bad-import-order,reimported,unused-variable

  configs = FLAGS.config or []
  # Override with --dataset and --model
  if FLAGS.dataset:
    configs.append("inputs.dataset_name='%s'" % FLAGS.dataset)
    if FLAGS.data_dir:
      configs.append("inputs.data_dir='%s'" % FLAGS.data_dir)
  if FLAGS.model:
    configs.append("train.model=@trax.models.%s" % FLAGS.model)
  gin.parse_config_files_and_bindings(FLAGS.config_file, configs)