@Override
  public final org.jdom2.Element addContent(Collection collection) {
    // ignore empty elements
    if (collection == null) {
      return null;
    }
    return super.addContent(collection);
  }
@ Override public final org . jdom2 . Element addContent ( Collection collection ) { if ( collection == null ) { return null ; } return super . addContent ( collection ) ; }
Appends all children in the given collection to the end of the content list. In event of an exception
during add the original content will be unchanged and the objects in the supplied collection will be unaltered.
@param collection Collection to append. Null values are ignored.
@return the element on which the method was called