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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 _notnull(expr):
 """ Return a sequence or scalar according to the input indicating if the values are not null. :param expr: sequence or scalar :return: sequence or scalar """


    if isinstance(expr, SequenceExpr):
        return NotNull(_input=expr, _data_type=types.boolean)
    elif isinstance(expr, Scalar):
        return NotNull(_input=expr, _value_type=types.boolean)