Set the epsilon for picking used by this artist
picker can be one of the following:
None: picking is disabled for this artist (default)
A boolean: if True then picking will be enabled and the artist will fire a pick event if the mouse event is over the artist
A float: if picker is a number it is interpreted as an epsilon tolerance in points and the artist will fire off an event if it’s data is within epsilon of the mouse event. For some artists like lines and patch collections, the artist may provide additional data to the pick event that is generated, e.g., the indices of the data within epsilon of the pick event
A function: if picker is callable, it is a user supplied function which determines whether the artist is hit by the mouse event:hit, props = picker(artist, mouseevent)
to determine the hit test. if the mouse event is over the artist, return hit=True and props is a dictionary of properties you want added to the PickEvent attributes.