fluid code support string type

x2paddle/core/fluid_code.py

@@ -35,25 +35,30 @@ class Layer(object):
         if isinstance(self.inputs, list):
             in_list = "["
             for input in self.inputs:
-                assert isinstance(
-                    input, GraphNode), "Type of input should be GraphNode"
+                if isinstance(input, GraphNode):
                     if hasattr(input, "index"):
-                    in_list += (input.layer_name + "[{}]".format(input.index) +
-                                ", ")
+                        in_list += (input.layer_name + "[{}]".format(input.index) + ", ")
                     else:
                         in_list += (input.layer_name + ", ")
+                elif isinstance(input, str):
+                    in_list += (input + ", ")
+                else:
+                    raise Exception("Element of inputs should GraphNode or String")
             in_list = in_list.strip(", ") + "], "
             layer_code += in_list
         elif isinstance(self.inputs, dict):
             for key, input in self.inputs.items():
-                assert isinstance(
-                    input, GraphNode), "Type of input should be GraphNode"
+                if isinstance(input, GraphNode):
                     if hasattr(input, "index"):
                         layer_code = layer_code + key + "={}, ".format(
                             input.layer_name + "[{}]".format(input.index))
                     else:
                         layer_code = layer_code + key + "={}, ".format(
                             input.layer_name)
+                elif isinstance(input, str):
+                    layer_code = layer_code + key + "={}, ".format(input)
+                else:
+                    raise Exception("Element of inputs should GraphNode or String")
         elif isinstance(self.inputs, GraphNode):
             if hasattr(self.inputs, "index"):
                 layer_code += (self.inputs.layer_name +