code: def pretty_diff(self, mail_a, mail_b):
          
          return ''.join(unified_diff(
              mail_a.body_lines, mail_b.body_lines,
              fromfile='Normalized body of {}'.format(mail_a.path),
              tofile='Normalized body of {}'.format(mail_b.path),
              fromfiledate='{:0.2f}'.format(mail_a.timestamp),
              tofiledate='{:0.2f}'.format(mail_b.timestamp),
              n=0, lineterm='\n'))
docs: Returns a verbose unified diff between two mails' normalized body.