public MethodSymbols GetFunctionSymbols(RuntimeFunction function)
        {
            MethodSymbols symbols;
            if (!_cachedSymbols.TryGetValue(function.Token, out symbols))
            {
                var symMethod = GetSymMethod(function.Token);
                if (symMethod == null)
                    return null;

                _cachedSymbols.Add(function.Token, symbols = new MethodSymbols(function, symMethod));
            }

            return symbols;
        }