code: def BETWEEN(a, b):
      
      if any((isinstance(x, ConditionalElement) for x in (a, b))):
          raise TypeError(
              "A ConditionalElement can't be used as an operator condition.")
      else:
          return P(lambda x: a <= x <= b)
docs: The BETWEEN operator selects values within a given range.
      The BETWEEN operator is inclusive: begin and end values are included.