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