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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):
 """ This attribute retrieve the url that will be used as a HTTP request to the Crossref API. This attribute can be used compounded with query, filter, sort, order and facet methods. Examples: 'https://api.crossref.org/works?query=zika' 'https://api.crossref.org/works?query=zika&filter=prefix%3A10.1590' 'https://api.crossref.org/works?sort=published&order=desc&query=zika&filter=prefix%3A10.1590' 'https://api.crossref.org/works?sort=published&filter=prefix%3A10.1590%2Chas-abstract%3Atrue&query=zika&order=desc&query.author=Marli' """

        request_params = self._escaped_pagging()

        sorted_request_params = sorted([(k, v) for k, v in request_params.items()])
        req = requests.Request(
            'get', self.request_url, params=sorted_request_params).prepare()

        return req.url