code: def k_array_rank_jit(a):
      
      k = len(a)
      idx = a[0]
      for i in range(1, k):
          idx += comb_jit(a[i], i+1)
      return idx
docs: Numba jit version of `k_array_rank`.
  
      Notes
      -----
      An incorrect value will be returned without warning or error if
      overflow occurs during the computation. It is the user's
      responsibility to ensure that the rank of the input array fits
      within the range of possible values of `np.intp`; a sufficient
      condition for it is `scipy.special.comb(a[-1]+1, len(a), exact=True)
      <= np.iinfo(np.intp).max`.