Returns the first index of the element within the collection, or -1 if not found.
Note: A collection will not contain any duplicate items. All items within a collection are unique.
var shapes = Pablo(),
shapeA = Pablo.circle(),
shapeB = Pablo.rect(),
shapeC = Pagitblo.ellipse();
shapes.push([shapeA, shapeB, shapeC]);
alert(shapes.indexOf(shapeA));