def METHOD_NAME(self):
    array = self.create(f0=0, df=1)
    # test simple
    array2 = array.crop_frequencies()
    utils.assert_quantity_sub_equal(array, array2)
    assert numpy.may_share_memory(array.value, array2.value)
    # test normal
    array2 = array.crop_frequencies(2, 5)
    utils.assert_array_equal(array2.value, array.value[:, 2:5])
    assert array2.f0 == 2 * units.Hertz
    assert array2.df == array.df
    # test copy
    array2 = array.crop_frequencies(copy=True)
    assert not numpy.may_share_memory(array.value, array2.value)
    # test warnings
    with pytest.warns(UserWarning):
        array.crop_frequencies(array.yspan[0]-1, array.yspan[1])
    with pytest.warns(UserWarning):
        array.crop_frequencies(array.yspan[0], array.yspan[1]+1)