code: def spmt(t, peak_delay=6, under_delay=16, peak_disp=1, under_disp=1,
           p_u_ratio=6):
      
      return spm_hrf_compat(t, peak_delay=peak_delay, under_delay=under_delay,
                            peak_disp=peak_disp, under_disp=under_disp,
                            p_u_ratio=p_u_ratio, normalize=True)
docs: Normalized SPM HRF function from sum of two gamma PDFs
  
      Parameters
      ----------
      t : array-like
          vector of times at which to sample HRF
  
      Returns
      -------
      hrf : array
          vector length ``len(t)`` of samples from HRF at times `t`
  
      Notes
      -----
      [1] This is the canonical HRF function as used in SPM. It
      has the following defaults:
          - delay of response (relative to onset) : 6s
          - delay of undershoot (relative to onset) : 16s
          - dispersion of response : 1s
          - dispersion of undershoot : 1s
          - ratio of response to undershoot : 6s
          - onset : 0s
          - length of kernel : 32s
  
      References:
      -----
      [1] http://nipy.org/
      [2] https://github.com/fabianp/hrf_estimation