code: def _lbeta(x):
      return sum_mod.sum(lgamma.lgamma(x), axis=-1) - lgamma.lgamma(
          sum_mod.sum(x, axis=-1)
      )
  
imports: import numpy
  import chainer
  from chainer import distribution
  from chainer.functions.array import expand_dims
  from chainer.functions.math import digamma
  from chainer.functions.math import exponential
  from chainer.functions.math import lgamma
  from chainer.functions.math import sum
  from chainer.utils import cache
label_desc: Use image node_id 1 for calling a global function with example usage: _lbeta(x) and returns: unknown