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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, filename, external=False):
        '''
        This function gets the URL a file uploaded to this set would be
        accessed at. It doesn't check whether said file exists.

        :param string filename: The filename to return the URL for.
        :param bool external: If True, returns an absolute URL
        '''
        if filename.startswith('/'):
            filename = filename[1:]
        if self.has_url:
            return self.base_url + filename
        else:
            return url_for('fs.get_file', fs=self.name, filename=filename, _external=external)