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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 _create_request_schema(self, params, required):
 """Create a JSON schema for a request. :param list params: A list of keys specifying which definitions from the base schema should be allowed in the request. :param list required: A subset of the params that the requester must specify in the request. :returns: a JSON schema dict """

        # We allow additional properties because the data this will validate
        # may also include kwargs passed by decorators on the handler method.
        schema = {'additionalProperties': True,
                  'definitions': self.resolve('#/definitions'),
                  'properties': {},
                  'required': required or (),
                  'type': 'object'}
        for param in params:
            schema['properties'][param] = {
                '$ref': '#/definitions/{}'.format(param)}
        return schema