code: def _kernel_matrix(x, kernel):
      """Return RBFs, with centers at `x`, evaluated at `x`."""
      out = cp.empty((x.shape[0], x.shape[0]), dtype=float)
      kernel_func = NAME_TO_FUNC[kernel]
      kernel_matrix(x, kernel_func, 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 1 for calling a global function with example usage: _kernel_matrix(x, kernel) and returns: out