code: public final IonTextWriterBuilder
      withInitialIvmHandling(InitialIvmHandling handling)
      {
          IonTextWriterBuilder b = mutable();
          b.setInitialIvmHandling(handling);
          return b;
      }
docs: Declares the strategy for emitting Ion version markers at the start
  of the stream, returning a new mutable builder if this is immutable.
  By default, IVMs are emitted only when explicitly
  written or when necessary (for example, before data that's not Ion 1.0).
  
  @param handling the initial IVM strategy.
  Null indicates that explicitly-written IVMs will be emitted.
  
  @return this instance, if mutable;
  otherwise a mutable copy of this instance.
  
  @see #setInitialIvmHandling(IonWriterBuilder.InitialIvmHandling)
  @see #withInitialIvmHandling(IonWriterBuilder.InitialIvmHandling)