code: def distance(self, other_or_start=None, end=None, features=False):
          
          if end is None:
              assert other_or_start.chrom == self.chrom
  
          other_start, other_end = get_start_end(other_or_start, end)
  
          if other_start > self.end:
              return other_start - self.end
          if self.start > other_end:
              return self.start - other_end
          return 0
docs: check the distance between this an another interval
          Parameters
          ----------
  
          other_or_start : Interval or int
              either an integer or an Interval with a start attribute indicating
              the start of the interval
  
          end : int
              if `other_or_start` is an integer, this must be an integer
              indicating the end of the interval
  
          features : bool
              if True, the features, such as CDS, intron, etc. that this feature
              overlaps are returned.