code: def turningpoint(self):
          
          coefs = self.coefs
          old_dc = coefs[1]-coefs[0]
          for idx in range(self.order-2):
              new_dc = coefs[idx+2]-coefs[idx+1]
              if (old_dc < 0.) and (new_dc > old_dc):
                  return idx, coefs[idx]
              old_dc = new_dc
          raise RuntimeError(
              'Not able to detect a turning point in the impulse response '
              'defined by the MA coefficients %s.'
              % objecttools.repr_values(coefs))
docs: Turning point (index and value tuple) in the recession part of the
          MA approximation of the instantaneous unit hydrograph.