ProgramNode(0...14)(
  [],
  StatementsNode(0...14)(
    [InterpolatedStringNode(0...14)(
       (0...4),
       [StringNode(5...7)(nil, (5...7), nil, "a\n"),
        EmbeddedStatementsNode(7...11)(
          (7...9),
          StatementsNode(9...10)(
            [CallNode(9...10)(nil, nil, (9...10), nil, nil, nil, nil, 0, "b")]
          ),
          (10...11)
        ),
        StringNode(11...12)(nil, (11...12), nil, "\n")],
       (12...14)
     )]
  )
)
