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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 is_valid(cls, oid):
 """Checks if a `oid` string is valid or not. :Parameters: - `oid`: the object id to validate .. versionadded:: 2.3 """

        if not oid:
            return False

        try:
            ObjectId(oid)
            return True
        except (InvalidId, TypeError):
            return False