'Test deleting a slice of cards from the header.'

def test_header_slice_delete(self):

    header = fits.Header([('A', 'B'), ('C', 'D'), ('E', 'F')])
    del header[1:]
    assert (len(header) == 1)
    assert (header[0] == 'B')
    del header[:]
    assert (len(header) == 0)
