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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 datetime_from_isoformat(value: str):
 """Return a datetime object from an isoformat string. Args: value (str):
 Datetime string in isoformat. """

    if sys.version_info >= (3, 7):
        return datetime.fromisoformat(value)

    return datetime.strptime(value, '%Y-%m-%dT%H:%M:%S.%f')