code: def check_forward(self, x1_data, x2_data):
      y = F.arctan2(x1_data, x2_data)
      numpy.testing.assert_array_less(
          cuda.to_cpu(y.data), numpy.full(y.shape, numpy.pi)
      )
      numpy.testing.assert_array_less(
          numpy.full(y.shape, -numpy.pi), cuda.to_cpu(y.data)
      )
      testing.assert_allclose(
          numpy.arctan2(self.x1, self.x2), y.data, atol=1e-4, rtol=1e-4
      )
  
imports: import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  import chainer.functions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 2 for calling the TestArctan2 obj's underlying member method code with example usage: obj.check_forward(x1_data, x2_data) without return types