code: @Nonnull
      public BugInstance addMethod(PreorderVisitor visitor) {
          MethodAnnotation methodAnnotation = MethodAnnotation.fromVisitedMethod(visitor);
          addMethod(methodAnnotation);
          addSourceLinesForMethod(methodAnnotation, SourceLineAnnotation.fromVisitedMethod(visitor));
          return this;
      }
docs: Add a method annotation for the method which the given visitor is
  currently visiting. If the method has source line information, then a
  SourceLineAnnotation is added to the method.
  
  @param visitor
  the BetterVisitor
  @return this object