code: def _polynomial_matrix(x, powers):
      """Return monomials, with exponents from `powers`, evaluated at `x`."""
      out = cp.empty((x.shape[0], powers.shape[0]), dtype=float)
      polynomial_matrix(x, powers, out)
      return out
  
imports: import pickle
  import pytest
  import warnings
  import numpy
  from numpy.linalg import LinAlgError
  import cupy
  import cupyx
  from cupy import testing
  import cupyx.scipy.interpolate
  from cupyx.scipy.interpolate._rbfinterp import _AVAILABLE, _SCALE_INVARIANT, _NAME_TO_MIN_DEGREE, NAME_TO_FUNC, _monomial_powers, polynomial_matrix, kernel_matrix
label_desc: Use image node_id 2 for calling a global function with example usage: _polynomial_matrix(x, powers) and returns: out