code: def test_selection_rate_single_element(y_true, y_pred, expected):
      assert expected == metrics.selection_rate(y_true, y_pred)
  
imports: import pytest
  import fairlearn.metrics
  from fairlearn.metrics._base_metrics import _EMPTY_INPUT_PREDICTIONS_ERROR_MESSAGE
label_desc: Use image node_id 2 for calling a global function with example usage: test_selection_rate_single_element(y_true, y_pred, expected) without return types