Picker for the case of multiple points3d objects

Hello,
Following the official examples and want to be able to extract the x,y,z coordinates of a clicked sphere glyph made by points3d() in a 3-D scene. Where my application differs is that I have multiple (indeed, a Python list) of mlab.points3d objects. The standard example allows for identifying the index number of a particular sphere in a single points3d object. Do I need separate pickers defined for each points3d() object? How would I control which picker gets triggered?