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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def metamodel_from_str(lang_desc, metamodel=None, **kwargs):
 """ 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. """


    if not metamodel:
        metamodel = TextXMetaModel(**kwargs)

    language_from_str(lang_desc, metamodel)

    return metamodel