def setup_default_session(**kwargs):
    """
    Set up a default session, passing through any parameters to the session
    constructor. There is no need to call this unless you wish to pass custom
    parameters, because a default session will be created for you.
    """
    global DEFAULT_SESSION
    DEFAULT_SESSION = Session(**kwargs)

    Set up a default session, passing through any parameters to the session
    constructor. There is no need to call this unless you wish to pass custom
    parameters, because a default session will be created for you.
    
boto3/__init__.py