def find_test_index(test, selected_tests, find_last_index=False):
    """Find the index of the first or last occurrence of a given test/test module in the list of selected tests.

    This function is used to determine the indices when slicing the list of selected tests when
    ``options.first``(:attr:`find_last_index`=False) and/or ``options.last``(:attr:`find_last_index`=True) are used.

    :attr:`selected_tests` can be a list that contains multiple consequent occurrences of tests
    as part of the same test module, e.g.:

    ```
    selected_tests = ['autograd', 'cuda', **'torch.TestTorch.test_acos',
                     'torch.TestTorch.test_tan', 'torch.TestTorch.test_add'**, 'utils']
    ```

    If :attr:`test`='torch' and :attr:`find_last_index`=False, result should be **2**.
    If :attr:`test`='torch' and :attr:`find_last_index`=True, result should be **4**.

    Args:
        test (str): Name of test to lookup
        selected_tests (list): List of tests
        find_last_index (bool, optional): should we lookup the index of first or last
            occurrence (first is default)

    Returns:
        index of the first or last occurrence of the given test
    """
    idx = 0
    found_idx = -1
    for t in selected_tests:
        if t.startswith(test):
            found_idx = idx
            if not find_last_index:
                break
        idx += 1
    return found_idx