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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_datetime(cls, generation_time):
 """Create a dummy ObjectId instance with a specific generation time. This method is useful for doing range queries on a field containing :class:`ObjectId` instances. .. warning:: It is not safe to insert a document containing an ObjectId generated using this method. This method deliberately eliminates the uniqueness guarantee that ObjectIds generally provide. ObjectIds generated with this method should be used exclusively in queries. `generation_time` will be converted to UTC. Naive datetime instances will be treated as though they already contain UTC. An example using this helper to get documents where ``"_id"`` was generated before January 1, 2010 would be: :Parameters: - `generation_time`: :class:`~datetime.datetime` to be used as the generation time for the resulting ObjectId. """

        if generation_time.utcoffset() is not None:
            generation_time = generation_time - generation_time.utcoffset()
        timestamp = calendar.timegm(generation_time.timetuple())
        oid = struct.pack(
            ">i", int(timestamp)) + b"\x00\x00\x00\x00\x00\x00\x00\x00"
        return cls(oid)