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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 url(self):
 """ Constructs and returns the View URL. :returns: View URL """

        if self._partition_key:
            base_url = self.design_doc.document_partition_url(
                self._partition_key)
        else:
            base_url = self.design_doc.document_url

        return '/'.join((
            base_url,
            '_view',
            self.view_name
        ))