Custom compositor node - connecting input to output

Question

I am trying to make this simple node group that would simply connect the input to the output so it would simply repeat an image like below.

What is the problem with my code? It's like nothing is coming out from the output.

import bpy

class Repeat (bpy.types.NodeCustomGroup):

    bl_name='Repeat'
    bl_label='Repeat'           

    def init(self, context):
        self.node_tree=bpy.data.node_groups.new(self.bl_name, 'CompositorNodeTree')
        if hasattr(self.node_tree, 'is_hidden'):
            self.node_tree.is_hidden=True

        self.node_tree.inputs.new("NodeSocketColor", "Image")
        self.node_tree.outputs.new("NodeSocketColor", "Image")
        self.node_tree.nodes.new('NodeGroupInput')
        self.node_tree.nodes.new('NodeGroupOutput') 

        #trying to connect input to output here, possible problem?
        self.node_tree.links.new(self.node_tree.nodes['Group Input'].outputs[0],self.node_tree.nodes['Group Output'].inputs[0])

    def free(self):
        bpy.data.node_groups.remove(self.node_tree, do_unlink=True)

from nodeitems_utils import NodeItem, register_node_categories, unregister_node_categories
from nodeitems_builtins import CompositorNodeCategory

def register():
    bpy.utils.register_class(Repeat)
    newcatlist = [CompositorNodeCategory("CP_GENERATE", "Testing", items=[NodeItem("Repeat"),]),]
    register_node_categories("GENERATE_NODES", newcatlist)

def unregister():
    unregister_node_categories("GENERATE_NODES")
    bpy.utils.unregister_class(Repeat)

try :
    unregister()
except:
    pass
register()