AIMA.Core.Logic.Propositional.Parsing.Ast.Sentence.accept C# (CSharp) Method

        public abstract Object accept(PLVisitor plv, Object arg);
    }

 public List<Symbol> getSymbolsIn(Sentence s)
 {
     if (s == null)
     {// empty knowledge bases == null fix this later
         return new List<Symbol>();
     }
     return (List<Symbol>)s.accept(this, new List<Symbol>());
 }