'Add a :class:`~matplotlib.collections.Collection` instance
to the axes.
Returns the collection.'

def add_collection(self, collection, autolim=True):

    label = collection.get_label()
    if (not label):
        collection.set_label((u'_collection%d' % len(self.collections)))
    self.collections.append(collection)
    self._set_artist_props(collection)
    if (collection.get_clip_path() is None):
        collection.set_clip_path(self.patch)
    if autolim:
        self.update_datalim(collection.get_datalim(self.transData))
    collection._remove_method = (lambda h: self.collections.remove(h))
    self.stale = True
    return collection
