docs: def fit_traptransit(ts,fs,p0):
      """
      Fits trapezoid model to provided ts,fs
      """
      pfit,success = leastsq(traptransit_resid,p0,args=(ts,fs))
      if success not in [1,2,3,4]:
          raise NoFitError
      #logging.debug('success = {}'.format(success))
      return pfit