fix gradient node (with more cofee)

MaterialGraphProject/Assets/Eduardo/FunctionNInNOut.cs

                 ")";
         }
 
-        private string GetFunctionCall(GenerationMode generationMode)
+
+        protected virtual string GetFunctionCall(GenerationMode generationMode)
         {
             string prefix = "";
             string sufix = "";
             var outputString = new ShaderGenerator();
             outputString.AddShaderChunk(GetOutputDeclaration(), false);
             outputString.AddShaderChunk(GetFunctionCall(generationMode), false);
-
+             
             visitor.AddShaderChunk(outputString.GetShaderString(0), true);
         }
 

MaterialGraphProject/Assets/_MingWai/GradientNode.cs

             get { return true; }
         }
 
-        protected virtual string GetFunctionCall(GenerationMode generationMode)
+        protected override string GetFunctionCall(GenerationMode generationMode)
         {
             //here we don't want to generate final value as the parameters are used as output
             //TODO allow to define parameters as ouput in the function prototype and handle