======= AST Display =========================
Package
  ClassDeclList [1]
  . ClassDecl
  .   "id" classname
  .   FieldDeclList [0]
  .   MethodDeclList [1]
  .   . (public static) MethodDecl
  .   .   VOID BaseType
  .   .   "main" methodname
  .   .   ParameterDeclList [1]
  .   .   . ParameterDecl
  .   .   .   ArrayType
  .   .   .     ClassType
  .   .   .       "String" classname
  .   .   .   "args"parametername 
  .   .   StmtList [0]
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