code: def test_rfft_overwrite_plan(self, xp, scp, dtype):
      x = testing.shaped_random(self.shape, xp, dtype)
      if scp is cupyx.scipy:
          plan = scp.fftpack.get_fft_plan(
              x, shape=self.n, axes=self.axis, value_type="R2C"
          )
          x = scp.fftpack.rfft(
              x, n=self.n, axis=self.axis, overwrite_x=True, plan=plan
          )
      else:  # scipy
          x = scp.fftpack.rfft(
              x, n=self.n, axis=self.axis, overwrite_x=True
          )
      return x
  
imports: import unittest
  import numpy
  import pytest
  import cupy
  from cupy import testing
  import cupyx.scipy.fftpack
  from cupy.fft._fft import _default_fft_func, _fftn
label_desc: Use image node_id 4 for calling the TestRfft obj's underlying member method code with example usage: obj.test_rfft_overwrite_plan(xp, scp, dtype) and returns: x