def add_property(accessor, predicate, object)
      new_property = RDF::Statement.new(bnode, predicate, object)
      attributes_list[accessor] = new_property
    end
def add_property(accessor, predicate, object)
      new_property = RDF::Statement.new(bnode, predicate, object)
      attributes_list[accessor] = new_property
    end
Add a property without defining it on the class.
 This will stay, will use the subject, and the regular infrastructure.
 @param [Symbol] accessor, the new field being created.
 @param [RDF::Statement] predicate, the predicate for the new field.
 @param [Any] The value to store