title: Convert list of MultiPolygons and Polygons to a single MultiPolygon
body: <p>How do I create in a generic manner a MultiPolygon from a list of MultiPolygon and Polygon objects?</p>
  
  <pre><code>a = MultiPolygon([Polygon([(0, 0), (1, 1), (1, 0)])])
  b = Polygon([(0, 0), (2, 1), (1, 0)])
  </code></pre>
  
  <p>I wish to perform an operation that results in the following object:</p>
  
  <pre><code>MultiPolygon([Polygon([(0, 0), (1, 1), (1, 0)]) , Polygon([(0, 0), (2, 1), (1, 0)])])
  </code></pre>
  
  <p>I'm not looking to create a union, I just wish to iterate all the polygons. </p>