'Return the ring at the specified index. The first index, 0, will
always return the exterior ring.  Indices > 0 will return the
interior ring at the given index (e.g., poly[1] and poly[2] would
return the first and second interior ring, respectively).
CAREFUL: Internal/External are not the same as Interior/Exterior!
Return a pointer from the existing geometries for use internally by the
object\'s methods. _get_single_external() returns a clone of the same
geometry for use by external code.'

def _get_single_internal(self, index):

    if (index == 0):
        return capi.get_extring(self.ptr)
    else:
        return capi.get_intring(self.ptr, (index - 1))
