code: def circularize(self):
          '''Circularize linear DNA.
  
          :returns: A circularized version of the current sequence.
          :rtype: coral.DNA
  
          '''
          if self.top[-1].seq == '-' and self.bottom[0].seq == '-':
              raise ValueError('Cannot circularize - termini disconnected.')
          if self.bottom[-1].seq == '-' and self.top[0].seq == '-':
              raise ValueError('Cannot circularize - termini disconnected.')
  
          copy = self.copy()
          copy.circular = True
          copy.top.circular = True
          copy.bottom.circular = True
          return copf circularize(self):
          '''Circularize linear DNA.
  
          :returns: A circularized version of the current sequence.
          :rtype: coral.DNA
  
          '''
          if self.top[-1].seq == '-' and self.bottom[0].seq == '-':
              raise ValueError('Cannot circularize - termini disconnected.')
          if self.bottom[-1].seq == '-' and self.top[0].seq == '-':
              raise ValueError('Cannot circularize - termini disconnected.')
  
          copy = self.copy()
          copy.circular = True
          copy.top.circular = True
          copy.bottom.circular = True
          return copy
docs: Circularize linear DNA.
  
          :returns: A circularized version of the current sequence.
          :rtype: coral.DNA