code: import numpy as np
  import itertools
  from nptyping import NDArray
  from typing import Iterator
  from ..objective import Objective
  
  
  def powerset(f: Objective) -> Iterator[NDArray[int]]:
      """
      Inumerate b^n possible vectors in the integer lattice.
      :param f: integer-lattice submodular function objective
      """
      return map(lambda t: np.array([*t]),
                 itertools.product(range(f.b + 1), repeat=f.n))
  
apis: numpy.array