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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 from_aid(cls, aid):
 """Retrieve the Assay record for the specified AID. :param int aid: The PubChem Assay Identifier (AID). """

        record = json.loads(request(aid, 'aid', 'assay', 'description').read().decode())['PC_AssayContainer'][0]
        return cls(record)