new_contents: from __future__ import division, absolute_import, print_function
  
  import numpy as np
  
  try:
      from scipy.signal import lfilter, firwin
  except ImportError:
      pass
  
  from .common import Benchmark
  
  
  class Lfilter(Benchmark):
      param_names = ['n_samples', 'numtaps']
      params = [
          [1e3, 50e3, 1e6],
          [9, 23, 51]
      ]
  
      def setup(self, n_samples, numtaps):
          np.random.seed(125678)
          sample_rate = 25000.
          t = np.arange(n_samples, dtype=np.float64) / sample_rate
          nyq_rate = sample_rate / 2.
          cutoff_hz = 3000.0
          self.sig = np.sin(2*np.pi*500*t) + 0.3 * np.sin(2*np.pi*11e3*t)
          self.coeff = firwin(numtaps, cutoff_hz/nyq_rate)
  
  
      def time_lfilter(self, n_samples, numtaps):
          lfilter(self.coeff, 1.0, self.sig)
  
subject: add benchmark for signal.lfilter. Follow-up of gh-4628.