https://www.graalvm.org/ 
final class com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage extends com.oracle.truffle.api.TruffleLanguage$LanguageReference<com.oracle.truffle.api.TruffleLanguage<java.lang.Object>>
  minor version: 0
  major version: 59
  flags: flags: (0x0030) ACC_FINAL, ACC_SUPER
  this_class: com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage
  super_class: com.oracle.truffle.api.TruffleLanguage$LanguageReference
{
  private final com.oracle.truffle.api.TruffleLanguage$LanguageReference<com.oracle.truffle.api.TruffleLanguage<java.lang.Object>> singleLanguageReference;
    descriptor: Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL
    Signature: Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference<Lcom/oracle/truffle/api/TruffleLanguage<Ljava/lang/Object;>;>;

  private final com.oracle.truffle.api.TruffleLanguage$LanguageReference<com.oracle.truffle.api.TruffleLanguage<java.lang.Object>> fallbackReference;
    descriptor: Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL
    Signature: Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference<Lcom/oracle/truffle/api/TruffleLanguage<Ljava/lang/Object;>;>;

  private final com.oracle.truffle.api.Assumption singleLanguage;
    descriptor: Lcom/oracle/truffle/api/Assumption;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL

  void <init>(com.oracle.truffle.polyglot.PolyglotLanguage, com.oracle.truffle.polyglot.PolyglotLanguageInstance, com.oracle.truffle.api.Assumption, com.oracle.truffle.api.TruffleLanguage$LanguageReference<com.oracle.truffle.api.TruffleLanguage<java.lang.Object>>);
    descriptor: (Lcom/oracle/truffle/polyglot/PolyglotLanguage;Lcom/oracle/truffle/polyglot/PolyglotLanguageInstance;Lcom/oracle/truffle/api/Assumption;Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference;)V
    flags: (0x0000) 
    Code:
      stack=3, locals=5, args_size=5
        start local 0 // com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage this
        start local 1 // com.oracle.truffle.polyglot.PolyglotLanguage language
        start local 2 // com.oracle.truffle.polyglot.PolyglotLanguageInstance initValue
        start local 3 // com.oracle.truffle.api.Assumption singleContextAssumption
        start local 4 // com.oracle.truffle.api.TruffleLanguage$LanguageReference fallbackReference
         0: .line 343
            aload 0 /* this */
            invokespecial com.oracle.truffle.api.TruffleLanguage$LanguageReference.<init>:()V
         1: .line 344
            aload 0 /* this */
            aload 3 /* singleContextAssumption */
            putfield com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage.singleLanguage:Lcom/oracle/truffle/api/Assumption;
         2: .line 345
            aload 0 /* this */
            aload 1 /* language */
            aload 2 /* initValue */
            invokestatic com.oracle.truffle.polyglot.PolyglotReferences.createAlwaysSingleLanguage:(Lcom/oracle/truffle/polyglot/PolyglotLanguage;Lcom/oracle/truffle/polyglot/PolyglotLanguageInstance;)Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference;
            putfield com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage.singleLanguageReference:Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference;
         3: .line 346
            aload 0 /* this */
            aload 4 /* fallbackReference */
            putfield com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage.fallbackReference:Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference;
         4: .line 347
            return
        end local 4 // com.oracle.truffle.api.TruffleLanguage$LanguageReference fallbackReference
        end local 3 // com.oracle.truffle.api.Assumption singleContextAssumption
        end local 2 // com.oracle.truffle.polyglot.PolyglotLanguageInstance initValue
        end local 1 // com.oracle.truffle.polyglot.PolyglotLanguage language
        end local 0 // com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage this
      LocalVariableTable:
        Start  End  Slot                     Name  Signature
            0    5     0                     this  Lcom/oracle/truffle/polyglot/PolyglotReferences$AssumeSingleLanguage;
            0    5     1                 language  Lcom/oracle/truffle/polyglot/PolyglotLanguage;
            0    5     2                initValue  Lcom/oracle/truffle/polyglot/PolyglotLanguageInstance;
            0    5     3  singleContextAssumption  Lcom/oracle/truffle/api/Assumption;
            0    5     4        fallbackReference  Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference<Lcom/oracle/truffle/api/TruffleLanguage<Ljava/lang/Object;>;>;
    Signature: (Lcom/oracle/truffle/polyglot/PolyglotLanguage;Lcom/oracle/truffle/polyglot/PolyglotLanguageInstance;Lcom/oracle/truffle/api/Assumption;Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference<Lcom/oracle/truffle/api/TruffleLanguage<Ljava/lang/Object;>;>;)V
    MethodParameters:
                         Name  Flags
      language                 
      initValue                
      singleContextAssumption  
      fallbackReference        

  public com.oracle.truffle.api.TruffleLanguage<java.lang.Object> get();
    descriptor: ()Lcom/oracle/truffle/api/TruffleLanguage;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage this
         0: .line 351
            aload 0 /* this */
            getfield com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage.singleLanguage:Lcom/oracle/truffle/api/Assumption;
            invokeinterface com.oracle.truffle.api.Assumption.isValid:()Z
            ifeq 2
         1: .line 352
            aload 0 /* this */
            getfield com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage.singleLanguageReference:Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference;
            invokevirtual com.oracle.truffle.api.TruffleLanguage$LanguageReference.get:()Lcom/oracle/truffle/api/TruffleLanguage;
            areturn
         2: .line 354
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            getfield com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage.fallbackReference:Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference;
            invokevirtual com.oracle.truffle.api.TruffleLanguage$LanguageReference.get:()Lcom/oracle/truffle/api/TruffleLanguage;
            areturn
        end local 0 // com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    3     0  this  Lcom/oracle/truffle/polyglot/PolyglotReferences$AssumeSingleLanguage;
    Signature: ()Lcom/oracle/truffle/api/TruffleLanguage<Ljava/lang/Object;>;
}
Signature: Lcom/oracle/truffle/api/TruffleLanguage$LanguageReference<Lcom/oracle/truffle/api/TruffleLanguage<Ljava/lang/Object;>;>;
SourceFile: "PolyglotReferences.java"
NestHost: com.oracle.truffle.polyglot.PolyglotReferences
InnerClasses:
  public abstract LanguageReference = com.oracle.truffle.api.TruffleLanguage$LanguageReference of com.oracle.truffle.api.TruffleLanguage
  private final AssumeSingleLanguage = com.oracle.truffle.polyglot.PolyglotReferences$AssumeSingleLanguage of com.oracle.truffle.polyglot.PolyglotReferences