def register_default_action(self, file_pattern,  action_function):
if self.__default_action is not None:<EOL><INDENT>self.log_error('<STR_LIT>')<EOL><DEDENT>if not self.__is_function_action(action_function):<EOL><INDENT>self.log_error('<STR_LIT>')<EOL><DEDENT>self.__default_action = GeneratorAction(file_pattern=file_pattern, action_function=action_function)<EOL>
Default action used if no compatible action is found.

Args:
    file_pattern: A :program:`fnmatch` pattern for the files concerned by this action.
    action_function:

Warning:
    Be careful when defining a default action. This action is be applied to **all** template files for
    which no compatible action is found. You might want to prefer declare explicit actions than to rely on this
    implicit default action. Use at your own risks. That said, if you have lots of default cases, this
    default action can be very convenient and avoid lots of unnecessary action declarations.