Translation in Blender add-on

translation.py

import bpy

translation_dict = {
    "ja_JP": {("*", "key1"):"hoge"},
    "en_US": {("*", "key1"):"test"}}

class TranslationTestClass(bpy.types.Operator):
    bl_idname = "uv.translation_test"
    def execute(self, context):
        self.report({'INFO'}, bpy.app.translations.pgettext("key1"))
        return {'FINISHED'}

def register():
    bpy.utils.register_module(__name__)
    bpy.app.translations.register(__name__, translation_dict)

def unregister():
    bpy.utils.unregister_module(__name__)

if __name__ == "__main__":
    register()