code: def _is_twave(self, peak_num):
          
          i = self.peak_inds_i[peak_num]
  
          # Due to initialization parameters, last_qrs_ind may be negative.
          # No way to check in this instance.
          if self.last_qrs_ind - self.qrs_radius < 0:
              return False
  
          # Get half the qrs width of the signal to the left.
          # Should this be squared?
          sig_segment = normalize((self.sig_f[i - self.qrs_radius:i]
                                   ).reshape(-1, 1), axis=0)
          last_qrs_segment = self.sig_f[self.last_qrs_ind - self.qrs_radius:
                                        self.last_qrs_ind]
  
          segment_slope = np.diff(sig_segment)
          last_qrs_slope = np.diff(last_qrs_segment)
  
          # Should we be using absolute values?
          if max(segment_slope) < 0.5*max(abs(last_qrs_slope)):
              return True
          else:
              return False
docs: Check whether a segment is a t-wave. Compare the maximum gradient of
          the filtered signal segment with that of the previous qrs segment.
  
          Parameters
          ----------
          peak_num : int
              The peak number of the mwi signal where the qrs is detected