code: def ref_prelu(x, w, base_axis=1):
      wshape = [1 for _ in range(x.ndim)]
      if w.size != 1:
          wshape[base_axis] = w.size
      return np.maximum(0, x) + w.reshape(wshape) * np.minimum(0, x)
  
imports: import pytest
  import numpy
  import nnabla.functions
  from nbla_test_utils import list_context
label_desc: Use image node_id 1 for calling a global function with example usage: ref_prelu(x, w, base_axis) and returns: unknown