title: In JointJS, how an element accesses position, inPorts, outPorts?
body: <p>I am using jointJS for my academic project, I have such a question, How an element accesses position, inPorts, outPorts?
  For example, we create an element like this,</p>
  
  <pre><code>var m1 = new joint.shapes.devs.Model({
  position: { x: 50, y: 50 },
  size: { width: 90, height: 90 },
  inPorts: ['in1','in2'],
  outPorts: ['out'],
  attrs: {
      '.label': { text: 'Model', 'ref-x': .4, 'ref-y': .2 },
      rect: { fill: '#2ECC71' },
      '.inPorts circle': { fill: '#16A085' },
      '.outPorts circle': { fill: '#E74C3C' }
  }
  });
  graph.addCell(m1);
  </code></pre>
  
  <p>I want to get <code>position</code> and <code>inPorts</code> from <code>m1</code>, I have tried <code>m1( 'position' )</code> 
  and <code>m1.position()</code>
  , but it didn't work.</p>
  
  <p>Can someone solve this problem? Thank you in advance.</p>