Cell and auto_set_font_size() question

Hi,

I am new to Python and trying to use Cell and its method auto_set_font_size()

here is the code
"
def draw_Cell(self, lower, upper, node1, branch_name):

    c = Cell(lower, upper[0]-lower[0], upper[1] - lower[1],
               edgecolor='k', text = branch_name,
               facecolor= self.color_method(node1), loc = None)
   
    self.ax.add_patch(c)     

"
My question is how do I use the method ‘auto_set_font_size()’ to shrink font size to fit the text.

Thanks

Samir