code: def dspmt(t):
      
      t = np.asarray(t)
      return spmt(t) - spmt(t - 1)
docs: SPM canonical HRF derivative, HRF derivative values for time values `t`
  
      This is the canonical HRF derivative function as used in SPM.
  
      It is the numerical difference of the HRF sampled at time `t` minus the
      values sampled at time `t` -1