code: def test_empty_multidim(self, shape, axis):
      a = np.empty(shape, dtype=int)
      r = rankdata(a, axis=axis)
      expected_shape = (0,) if axis is None else shape
      assert_equal(r.shape, expected_shape)
      assert_equal(r.dtype, np.float64)
  
imports: import numpy
  from numpy.testing import assert_equal, assert_array_equal
  import pytest
  from scipy.stats import rankdata, tiecorrect
  from scipy._lib._util import np_long
label_desc: Use image node_id 2 for calling the TestRankData obj's underlying member method code with example usage: obj.test_empty_multidim(shape, axis) without return types