code: def calc_min_interval(x, alpha):
      
  
      n = len(x)
      cred_mass = 1.0 - alpha
  
      interval_idx_inc = int(np.floor(cred_mass * n))
      n_intervals = n - interval_idx_inc
      interval_width = x[interval_idx_inc:] - x[:n_intervals]
  
      if len(interval_width) == 0:
          print_('Too few elements for interval calculation')
          return [None, None]
  
      min_idx = np.argmin(interval_width)
      hdi_min = x[min_idx]
      hdi_max = x[min_idx + interval_idx_inc]
      return [hdi_min, hdi_max]
docs: Internal method to determine the minimum interval of
      a given width
  
      Assumes that x is sorted numpy array.