code: def internal_to_external_delta(self, internal_value, internal_delta):
          
  
          external_value = self.transformation.backward(internal_value)
          bound_internal = internal_value + internal_delta
          bound_external = self.transformation.backward(bound_internal)
          external_delta = bound_external - external_value
  
          return external_value, external_delta
docs: Transform an interval from the internal to the external reference (through the transformation). It is useful
          if you have for example a confidence interval in internal reference and you want to transform it to the
          external reference
  
          :param interval_value: value in internal reference
          :param internal_delta: delta in internal reference
          :return: value and delta in external reference