code: def _run(self, size, output_datatype=None, periodic=None):  # type: ignore
      ni, N_1 = np.arange(size), size
      if periodic == 0:
          N_1 = N_1 - 1
      alpha = 0.42
      beta = 0.08
      pi = np.pi
      y = np.cos((ni * (pi * 2)) / N_1) * (-0.5)
      y += np.cos((ni * (pi * 4)) / N_1) * beta
      y += alpha
      return self._end(size, y, output_datatype)
  
imports: import numpy
  from onnx.reference.ops._op_common_window import _CommonWindow
label_desc: Use image node_id 1 for calling the BlackmanWindow obj's underlying member method code with example usage: obj._run(size, output_datatype, periodic) and returns: self