def extract_arguments(text):
    """
    Returns the argument after the command.
    
    Examples:
    extract_arguments("/get name"): 'name'
    extract_arguments("/get"): ''
    extract_arguments("/get@botName name"): 'name'
    
    :param text: String to extract the arguments from a command
    :return: the arguments if `text` is a command (according to is_command), else None.
    """
    regexp = re.compile("/\w*(@\w*)*\s*([\s\S]*)",re.IGNORECASE)
    result = regexp.match(text)
    return result.group(2) if is_command(text) else None