'Load an IPython extension by its module name.'

@line_magic
def load_ext(self, module_str):

    if (not module_str):
        raise UsageError('Missing    module    name.')
    res = self.shell.extension_manager.load_extension(module_str)
    if (res == 'already    loaded'):
        print ('The    %s    extension    is    already    loaded.    To    reload    it,    use:' % module_str)
        print ('        %reload_ext', module_str)
    elif (res == 'no    load    function'):
        print ('The    %s    module    is    not    an    IPython    extension.' % module_str)
