Initialize a Grammars object from a json dictionary.

def _from_dict(cls, _dict):
        """Initialize a Grammars object from a json dictionary."""
        args = {}
        if 'grammars' in _dict:
            args['grammars'] = [
                Grammar._from_dict(x) for x in (_dict.get('grammars'))
            ]
        else:
            raise ValueError(
                'Required property \'grammars\' not present in Grammars JSON')
        return cls(**args)