THIS METHODS GETS CALLED BY SCENE, self referes to the instance of
Renders neurons and adds them to the scene.
:param neurons: list of names of neurons
:param alpha: float in range 0,1 - neurons transparency
:param pre: bool, if True the presynaptic sites of each neuron are
:param post: bool, if True the postsynaptic sites on each neuron are
:param colorby: str, criteria to use to color the neurons.
Accepts values like synapse_type, type, individual etc.
:param draw_patches: bool, default True. If true dark patches are used
to show the location of post synapses
:param draw_arrows: bool, default True. If true arrows are used to
show the location of post synapses