1. We will soon have LineCollection so we should probably add a class attribute to each Graphic subclass which is used by Plot when attaching all the graphic names as methods, since we'd want plot.line_collection() rather than plot.linecollection() and it maintains pep8 standards
2. It would be useful for Subplot.get_graphics() to return a dict instead of a list, where the keys are the object class.
   example:

from fastlotlib.graphics import ImageGraphic

graphics_in_subplot = gp[0, 0].get_graphics() 

graphics_in_subplot[ImageGraphic] # list of all `ImageGraphic` graphic instances within the subplot

@clewis7 thoughts?