code: def add_arg(self,arg, prepend=False):
          
  
          self.args = [arg_.strip() for arg_ in self.args if arg_.strip()]
  
          if arg.title() not in self.args:
              if prepend:
                  self.args = [arg.title()] + self.args
              else:
                  self.args.append(arg.title())
docs: Append an arg to the arg list