code: def validate(self):
          
          if not isinstance(self.field, LocalField):
              raise TypeError(u'Expected LocalField field, got: {} {}'.format(
                  type(self.field).__name__, self.field))
  
          if not isinstance(self.lower_bound, Expression):
              raise TypeError(u'Expected Expression lower_bound, got: {} {}'.format(
                  type(self.lower_bound).__name__, self.lower_bound))
  
          if not isinstance(self.upper_bound, Expression):
              raise TypeError(u'Expected Expression upper_bound, got: {} {}'.format(
                  type(self.upper_bound).__name__, self.upper_bound))
docs: Validate that the Between Expression is correctly representable.