code: function() {
      this._geom = _geom;
      this._tree = null;
      this._cache = {
        query: false,
        result: false
      };
      this._enabled = true;
    }
docs: Sigma Quad Constructor
  ----------------------
  
  The edgequad API as exposed to sigma.
   
  The edgequad core that will become the sigma interface with the quadtree.
  
  property {object} _tree     Property holding the quadtree object.
  property {object} _geom     Exposition of the _geom namespace for testing.
  property {object} _cache    Cache for the area method.
  property {boolean} _enabled Can index and retreive elements.