code: def test_invalid_bw():
      # GH4873
      x = np.arange(400)
      y = x**2
      with pytest.raises(ValueError):
          nparam.KernelReg(x, y, "c", bw=[12.5, 1.0])
  
imports: import pytest
  import numpy
  import numpy.testing
  import statsmodels.api
label_desc: Use image node_id 1 for calling a global function with example usage: test_invalid_bw() without return types