old_contents: # -*- coding: utf-8 -*-
  
  from scipy.signal import firwin, filtfilt
  
  
  def low_pass_filter(data, cutoff, fs, n_taps=255):
      """Apply low-pass filter
  
      Parameters
      ----------
      data : array, shape (`T`, `dim`)
          Array of sequence.
      cutoff : int,
          Cutoff frequency
      fs : int,
          Sampling frequency
      n_taps : int, optional
          Tap number
  
      Returns
      -------
      modified data: array, shape (`T`, `dim`)
          Array of modified sequence.
      """
      fil = firwin(n_taps, cutoff, pass_zero=True, nyq=fs//2)
      modified_data = filtfilt(fil, 1, data, axis=0)
      return modified_data
  
  
  def high_pass_filter(data, cutoff, fs, n_taps=255):
      """Apply high-pass filter
  
      Parameters
      ----------
      data : array, shape (`T`, `dim`)
          Array of sequence.
      cutoff : int,
          Cutoff frequency
      fs : int,
          Sampling frequency
      n_taps : int, optional
          Tap number
  
      Returns
      -------
      modified data: array, shape (`T`, `dim`)
          Array of modified sequence.
      """
      fil = firwin(n_taps, cutoff, pass_zero=False, nyq=fs//2)
      modified_data = filtfilt(fil, 1, data, axis=0)
      return modified_data
  
new_contents: # -*- coding: utf-8 -*-
  
  from scipy.signal import firwin, filtfilt
  
  
  def low_pass_filter(data, cutoff, fs, n_taps=255):
      """Apply low-pass filter
  
      Parameters
      ----------
      data : array, shape (`T`, `dim`)
          Array of sequence.
      cutoff : int,
          Cutoff frequency
      fs : int,
          Sampling frequency
      n_taps : int, optional
          Tap number
  
      Returns
      -------
      modified data: array, shape (`T`, `dim`)
          Array of modified sequence.
      """
      if data.shape[0] < n_taps * 3:
          raise ValueError(
              'Length of data should be three times longer than n_taps.')
  
      fil = firwin(n_taps, cutoff, pass_zero=True, nyq=fs//2)
      modified_data = filtfilt(fil, 1, data, axis=0)
      return modified_data
  
  
  def high_pass_filter(data, cutoff, fs, n_taps=255):
      """Apply high-pass filter
  
      Parameters
      ----------
      data : array, shape (`T`, `dim`)
          Array of sequence.
      cutoff : int,
          Cutoff frequency
      fs : int,
          Sampling frequency
      n_taps : int, optional
          Tap number
  
      Returns
      -------
      modified data: array, shape (`T`, `dim`)
          Array of modified sequence.
      """
      if data.shape[0] < n_taps * 3:
          raise ValueError(
              'Length of data should be three times longer than n_taps.')
  
      fil = firwin(n_taps, cutoff, pass_zero=False, nyq=fs//2)
      modified_data = filtfilt(fil, 1, data, axis=0)
      return modified_data
  
subject: add assertion to check data length for filtering