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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 ReplaceUserDefinedFunction(self, udf_link, udf, options=None):
 """Replaces a user defined function and returns it. :param str udf_link: The link to the user defined function. :param dict udf: :param dict options: The request options for the request. :return: The new UDF. :rtype: dict """

        if options is None:
            options = {}

        CosmosClient.__ValidateResource(udf)
        udf = udf.copy()
        if udf.get('serverScript'):
            udf['body'] = str(udf['serverScript'])
        elif udf.get('body'):
            udf['body'] = str(udf['body'])

        path = base.GetPathFromLink(udf_link)
        udf_id = base.GetResourceIdOrFullNameFromLink(udf_link)
        return self.Replace(udf,
                            path,
                            'udfs',
                            udf_id,
                            None,
                            options)