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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 _parse(cls, data, key=None):
 """ Parse a set of data to extract entity-only data. Use classmethod `parse` if available, otherwise use the `endpoint` class variable to extract data from a data blob. """

        parse = cls.parse if cls.parse is not None else cls.get_endpoint()

        if callable(parse):
            data = parse(data)
        elif isinstance(parse, str):
            data = data[key]
        else:
            raise Exception('"parse" should be a callable or string got, {0}'
                            .format(parse))
        return data