how to set latex options on graph to make them ultra small ?

edit

I am currently playing with functions indexed by unlabeled graphs. The following method (belonging to my parent class which models linear combinations of graphs) tells my parent how to print basis element indexed by a graph m (m is in fact an integer vector modeling a graph up to isomorphism).

 def _latex_term(self, m):
    r"""
    """
    G = m.to_graph()
    opt = G.latex_options()
    opt.set_option('tkz_style', 'Simple')
    opt.set_option('vertex_labels', False)
    opt.set_option('scale', 0.25)
    opt.set_option('vertex_size', 0.0)
    return '\mathcal{M}_{' + latex(G) + '}'

I tried to set the option 'vertex_size' to zero but the size of the vertex was not affected. I realize that some combinations of options can rapidly become incoherent. Currently, I do not manage to do smaller than in the copy-pasted proposition of code.

I just want a very small (but readable) unlabeled graph.