code: def to_string(self):
          '''
          API: to_string(self)
          Description:
          Returns string representation of node in dot language.
          Return:
              String representation of node.
          '''
          node = list()
          node.append(quote_if_necessary(str(self.name)))
          node.append(' [')
          flag = False
          for a in self.attr:
              flag = True
              node.append(a)
              node.append('=')
              node.append(quote_if_necessary(str(self.attr[a])))
              node.append(', ')
          if flag is True:
              node = node[:-1]
          node.append(']')
          return ''.join(nodef to_string(self):
          '''
          API: to_string(self)
          Description:
          Returns string representation of node in dot language.
          Return:
              String representation of node.
          '''
          node = list()
          node.append(quote_if_necessary(str(self.name)))
          node.append(' [')
          flag = False
          for a in self.attr:
              flag = True
              node.append(a)
              node.append('=')
              node.append(quote_if_necessary(str(self.attr[a])))
              node.append(', ')
          if flag is True:
              node = node[:-1]
          node.append(']')
          return ''.join(node)
docs: API: to_string(self)
          Description:
          Returns string representation of node in dot language.
          Return:
              String representation of node.