code: def flip(self):
          '''Flip the DNA - swap the top and bottom strands.
  
          :returns: Flipped DNA (bottom strand is now top strand, etc.).
          :rtype: coral.DNA
  
          '''
          copy = self.copy()
          copy.top, copy.bottom = copy.bottom, copy.top
          copy.features = [_flip_feature(f, len(self)) for f in copy.features]
          return copf flip(self):
          '''Flip the DNA - swap the top and bottom strands.
  
          :returns: Flipped DNA (bottom strand is now top strand, etc.).
          :rtype: coral.DNA
  
          '''
          copy = self.copy()
          copy.top, copy.bottom = copy.bottom, copy.top
          copy.features = [_flip_feature(f, len(self)) for f in copy.features]
          return copy
docs: Flip the DNA - swap the top and bottom strands.
  
          :returns: Flipped DNA (bottom strand is now top strand, etc.).
          :rtype: coral.DNA