public CharSequence sourceHeader() {
    if (this.sourceHeader == null) {
      String noImportsPragma = ImportRewriteDisabler.shouldDisableFor(this)
          ? Output.NO_IMPORTS
          : "";

      if (style().headerComments()) {
        Optional<DeclaringType> declaringType = constitution.protoclass().declaringType();
        if (declaringType.isPresent()) {
          CharSequence headerComments = declaringType.get().associatedTopLevel().headerComments();
          return !noImportsPragma.isEmpty()
              ? new StringBuilder(noImportsPragma).append('\n').append(headerComments)
              : headerComments;
        }
      }
      this.sourceHeader = noImportsPragma;
    }
    return sourceHeader;
  }
Should be called when it is known that there type adapters generation provided.
@return the type adapters annotation
value-processor/src/org/immutables/value/processor/meta/ValueType.java