code: def make_k_chose_e(e_vec, k_vec):
      
      return product([sp.factorial(k) / (sp.factorial(e) * sp.factorial(k - e)) for e,k in zip(e_vec, k_vec)])
docs: Computes the product :math:`{\mathbf{n} \choose \mathbf{k}}`
  
      :param e_vec: the vector e
      :type e_vec: :class:`numpy.array`
      :param k_vec: the vector k
      :type k_vec: :class:`numpy.array`
      :return: a scalar