code: def pywt_pad_mode(pad_mode, pad_const=0):
      
      pad_mode = str(pad_mode).lower()
      if pad_mode == 'constant' and pad_const != 0.0:
          raise ValueError('constant padding with constant != 0 not supported '
                           'for `pywt` back-end')
      try:
          return PAD_MODES_ODL2PYWT[pad_mode]
      except KeyError:
          raise ValueError("`pad_mode` '{}' not understood".format(pad_mode))
docs: Convert ODL-style padding mode to pywt-style padding mode.
  
      Parameters
      ----------
      pad_mode : str
          The ODL padding mode to use at the boundaries.
      pad_const : float, optional
          Value to use outside the signal boundaries when ``pad_mode`` is
          'constant'. Only a value of 0. is supported by PyWavelets
  
      Returns
      -------
      pad_mode_pywt : str
          The corresponding name of the requested padding mode in PyWavelets.
          See `signal extension modes`_.
  
      References
      ----------
      .. _signal extension modes:
         https://pywavelets.readthedocs.io/en/latest/ref/signal-extension-modes.html