Argh!! Can't wrap my head around this Python stuff!

[nospam.Greg Tibbet]

I'm an old timer, have programmed in Fortran, C, C++, Perl, and a bit of Java
and trying to learn this new-fangled Python language!

I've got a small program that uses PIL to create an image, draw some primitives
 (rectanges, ellipses, etc...) and save it.  Works fine... no issues.

I've found in the past, the best way to "really learn" the language was to "dig
 into the guts" and understand it,.. I thought I was making progress, but when
looking into the PIL library to see what's going on behind the scenes, I find
the following code in ImageDraw.py

def ellipse(self, xy, fill=None, outline=None):
        """Draw an ellipse."""
        ink, fill = self._getink(outline, fill)
        if fill is not None:
            self.draw.draw_ellipse(xy, fill, 1)
<...snipped...>

ellipse() uses the method  self.draw.draw_ellipse()   Okay, fine...
but WHERE is draw_ellipse defined??  What magic is happening there? I've
searched the entire PIL directory tree, and the ONLY two places draw_ellipse is
 mentioned are right there in the ellipse() function... WHAT am I missing??

Thanks!
-Stumpy (aka Greg)