code: def _vandermonde(x, degree):
      # Returns a matrix of monomials that span polynomials with the specified
      # degree evaluated at x.
      powers = _monomial_powers(x.shape[1], degree)
      return _polynomial_matrix(x, powers)
  
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 3 for calling a global function with example usage: _vandermonde(x, degree) and returns: _polynomial_matrix