code: def metamodel_from_str(lang_desc, metamodel=None, **kwargs):
      
  
      if not metamodel:
          metamodel = TextXMetaModel(**kwargs)
  
      language_from_str(lang_desc, metamodel)
  
      return metamodel
docs: Creates a new metamodel from the textX description given as a string.
  
      Args:
          lang_desc(str): A textX language description.
          metamodel(TextXMetaModel): A metamodel that should be used.
          other params: See TextXMetaModel.