code: def largest_loop(self):
          
          from collections import namedtuple
          Loop = namedtuple('Loop', 'start end')
          largest_segment = sorted(
                  self.loop_segments,
                  key=lambda x: abs(x[1] - x[0]),
          )[-1]
          return Loop(*largest_segment)
docs: Return the boundaries for the largest loop segment.
          
          This is just meant to be a reasonable default for various selectors and 
          filters to work with, in the case that more than one loop is being 
          modeled.  If you want to be more precise, you'll have to override the 
          selectors and filters in question.