code: def kernel_matrix(x, kernel_func, out):
      """Evaluate RBFs, with centers at `x`, at `x`."""
      delta = x[None, :, :] - x[:, None, :]
      out[...] = kernel_func(cp.linalg.norm(delta, axis=-1))
  
file_path: cupy/cupyx/scipy/interpolate/_rbfinterp.py
imports: import math
  import warnings
  from itertools import combinations_with_replacement
  import cupy
label_desc: Use image node_id 1 for calling a global function with example usage: kernel_matrix(x, kernel_func, out) without return types