docs: def variable_map_items(variable_map):
    """Yields an iterator over (string, variable) pairs in the variable map.
  
    In general, variable maps map variable names to either a `tf.Variable`, or
    list of `tf.Variable`s (in case of sliced variables).
  
    Args:
      variable_map: dict, variable map over which to iterate.
  
    Yields:
      (string, tf.Variable) pairs.
    """
    for key, var_or_vars in six.iteritems(variable_map):
      if isinstance(var_or_vars, (list, tuple)):
        for variable in var_or_vars:
          yield key, variable
      else:
        yield key, var_or_vars