code: def test_empty():
      """rankdata([]) should return an empty array."""
      a = np.array([], dtype=int)
      r = rankdata(a)
      assert_array_equal(r, np.array([], dtype=np.float64))
  
file_path: pynndescent/pynndescent/tests/test_rank.py
imports: import pytest
  import numpy
  from numpy.testing import assert_array_equal
  from pynndescent.distances import rankdata
label_desc: Use image node_id 1 for calling a global function with example usage: test_empty() without return types