code: def to_string(self):
          
  
          src = self.parse_node_ref( self.get_source() )
          dst = self.parse_node_ref( self.get_destination() )
          
          if isinstance(src, frozendict):
              edge = [ Subgraph(obj_dict=src).to_string() ]
          elif isinstance(src, (int, long)):
              edge = [ str(src) ]
          else:
              edge = [ src ]
          
          if	(self.get_parent_graph() and
              self.get_parent_graph().get_top_graph_type() and
              self.get_parent_graph().get_top_graph_type() == 'digraph' ):
  
              edge.append( '->' )
              
          else:
              edge.append( '--' )
              
          if isinstance(dst, frozendict):
              edge.append( Subgraph(obj_dict=dst).to_string() )
          elif isinstance(dst, (int, long)):
              edge.append( str(dst) )
          else:
              edge.append( dst )
  
  
          edge_attr = list()
          
          for attr, value in self.obj_dict['attributes'].iteritems():
          
              if value is not None:
                  edge_attr.append( '%s=%s' % (attr, quote_if_necessary(value) ) )
              else:
                  edge_attr.append( attr )
  
          edge_attr = ', '.join(edge_attr)
          
          if edge_attr:
              edge.append( ' [' + edge_attr + ']' )
  
          return ' '.join(edge) + ';'
docs: Returns a string representation of the edge in dot language.