code: def register_function(self, function_name, function):
          
          my_info = self._get_module_info(self._module.module_full_name)
          my_info[function_name] = function
docs: Register a function for the module.
  
          The following functions can be registered
  
  
              ..  py:function:: content_function()
  
              Called to discover what modules a container is displaying.  This is
              used to determine when updates need passing on to the container and
              also when modules can be put to sleep.
  
              the function must return a set of module names that are being
              displayed.
  
              .. note::
  
                  This function should only be used by containers.
  
              ..  py:function:: urgent_function(module_names)
  
              This function will be called when one of the contents of a container
              has changed from a non-urgent to an urgent state.  It is used by the
              group module to switch to displaying the urgent module.
  
              ``module_names`` is a list of modules that have become urgent
  
              .. note::
  
                  This function should only be used by containers.