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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 get(self, uri):
        '''Get the content for the bodypart identified by the uri.
        '''
        if uri.startswith('cid:'):
            # Content-ID, so raise exception if not found.
            head, part = self.id_dict[uri[4:]]
            return StringIO.StringIO(part.getvalue())
        if self.loc_dict.has_key(uri):
            head, part = self.loc_dict[uri]
            return StringIO.StringIO(part.getvalue())
        return None