code: @Override
      public final void visit(final Attribute attribute) {
          attributes.add(attribute);
          if (ignoreable(attribute)) {
              return;
          }
          trimmedAttributes.add(attribute);
      }
docs: Visit an Attribute. Track the complete list of Attributes and a list
  trimmed by removing "ignoreable" attributes.
  
  @see GedObjectVisitor#visit(Attribute)