Cascaded Union
==============

  >>> from functools import partial
  >>> import random
  >>> from shapely.geometry import Point
  >>> from shapely.ops import cascaded_union

Use a partial function to make 100 points uniformly distributed in a 40x40 
box centered on 0,0.

  >>> r = partial(random.uniform, -20.0, 20.0)
  >>> points = [Point(r(), r()) for i in range(100)]

Buffer the points, producing 100 polygon spots

  >>> spots = [p.buffer(2.5) for p in points]

Perform a cascaded union of the polygon spots, dissolving them into a 
collection of polygon patches

  >>> cascaded_union(spots) # doctest: +ELLIPSIS
  <shapely.geometry.multipolygon.MultiPolygon object at 0x...>