code: def post_build(self, container_builder, container):
          
          app = container.get('ioc.extra.flask.app')
  
          app.config.update(container_builder.parameters.get('ioc.extra.flask.app.config'))
  
          if container.has('ioc.extra.jinja2'):
              # This must be an instance of jinja.ChoiceLoader
              # This code replace the flask specific jinja configuration to use
              # the one provided by the ioc.extra.jinja2 code
              jinja2 = container.get('ioc.extra.jinja2')
  
              jinja2.loader.loaders.append(app.create_global_jinja_loader())
  
              for name, value in app.jinja_env.globals.items():
                  if name not in jinja2.globals:
                      jinja2.globals[name] = value                
  
              for name, value in app.jinja_env.filters.items():
                  if name not in jinja2.filters:
                      jinja2.filters[name] = value                
  
              app.jinja_env = jinja2
docs: This method make sure the flask configuration is fine, and 
          check the if ioc.extra.jinja2 service is available. If so, the 
          flask instance will use this service, by keeping the flask template 
          loader and the one registered at the jinja2