code: def default_str(str_, default_str):
      """Returns :attr:`str_` if it is not `None` or empty, otherwise returns
      :attr:`default_str`.
  
      Args:
          str_: A string.
          default_str: A string.
  
      Returns:
          Either :attr:`str_` or :attr:`default_str`.
      """
      if str_ is not None and str_ != "":
          return str_
      else:
          return default_str
  
imports: from typing import List, Union
  import inspect
  import funcsigs
  from pydoc import locate
  import copy
  import collections
  import numpy
  import tensorflow
  from texar.tf.hyperparams import HParams
  from texar.tf.utils.dtypes import is_str, is_callable, compat_as_text, _maybe_list_to_array
label_desc: Use image node_id 19 for calling a global function with example usage: default_str(str_, default_str) and returns: str_, default_str