code: def _n_choose_k(n, k):
      """Computes nCk."""
      return (
          math.factorial(n)
          // math.factorial(k)
          // math.factorial(n - k)
      )
  
imports: import functools
  import math
  import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.internal import dtype_util
  from tensorflow_probability.python.internal import nest_util
  from tensorflow_probability.python.internal import prefer_static
  from tensorflow_probability.python.mcmc import diagnostic
  from tensorflow.python.util import nest
label_desc: Use image node_id 4 for calling a global function with example usage: _n_choose_k(n, k) and returns: unknown