title: What's the difference between Element setProperty and TitanVertex addProperty in Blueprints?
body: <p>What is the difference between the Blueprints methods <code>vertex.addProperty(key, value);</code> implemented in TitanVertex and <code>vertex.setProperty(key, value);</code> in Element?</p>
  
  <p>If there is a difference, how can I translate <code>addProperty</code> into <code>setProperty</code>?</p>