{-(Program
  (ExpressionStatements
    (Function
      (Identifier)
      (Params
        (Other "required_parameter"
          (Identifier))
        (Other "required_parameter"
          (Identifier)))
      (ExpressionStatements
        (Function
          (Identifier)
          (Params
            (Other "required_parameter"
              (Identifier))
            (Other "required_parameter"
              (Identifier)))
          (ExpressionStatements
            (FunctionCall
              (Identifier)
              (Identifier)
              (Identifier)))
          (ExpressionStatements
            (FunctionCall
              (Identifier)
              (Identifier)
              (Identifier))))))))-}