def filename_input(self, path_or_filename):
        '''
        Open and read input from a *path or filename*, and parse its content.
        
        If the filename is a directory, files that ends with .xtuml located
        somewhere in the directory or sub directories will be loaded as well.
        '''
        if os.path.isdir(path_or_filename):
            for path, _, files in os.walk(path_or_filename):
                for name in files:
                    if name.endswith('.xtuml'):
                        xtuml.ModelLoader.filename_input(self, os.path.join(path, name))
        else:
            xtuml.ModelLoader.filename_input(self, path_or_filename)
Open and read input from a *path or filename*, and parse its content.
        
        If the filename is a directory, files that ends with .xtuml located
        somewhere in the directory or sub directories will be loaded as well.