code: def add_arc(self, src, dst, char):
          
          assert type(src) == type(int()) and type(dst) == type(int()), \
              "State type should be integer."
          while src >= len(self.states) or dst >= len(self.states):
              self.add_state()
          self.states[src].arcs.append(SFAArc(src, dst, char))
docs: This function adds a new arc in a SFA state
          Args:
              src (int): The source state identifier
              dst (int): The destination state identifier
              char (str): The transition symbol
          Returns:
              None