code: def spm_betaln(z):
      """Log of the multivariate beta function of a vector.
      @NOTE this function computes across columns if `z` is a matrix
      """
      return special.gammaln(z).sum(axis=0) - special.gammaln(
          z.sum(axis=0)
      )
  
imports: import numpy
  from scipy import special
  from pymdp import utils
  from itertools import chain
label_desc: Use image node_id 12 for calling a global function with example usage: spm_betaln(z) and returns: unknown