code: def spa_tmplt_precondition(length, delta_f, kmin=0):
      
      global _prec
      if _prec is None or _prec.delta_f != delta_f or len(_prec) < length:
          v = numpy.arange(0, (kmin+length*2), 1.0) * delta_f
          v = numpy.power(v[1:len(v)], -7.0/6.0)
          _prec = FrequencySeries(v, delta_f=delta_f, dtype=float32)
      return _prec[kmin:kmin + length]
docs: Return the amplitude portion of the TaylorF2 approximant, used to precondition
      the strain data. The result is cached, and so should not be modified only read.