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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 open(self, url):
 """ Open a document at the specified url. @param url: A document URL. @type url: str @return: A file pointer to the document. @rtype: StringIO """

        protocol, location = self.split(url)
        if protocol == self.protocol:
            return self.find(location)
        else:
            return None