Returns a mongo library for the given connection string

    Parameters
    ---------
    connection_string: `str`
        Format must be one of the following:
            library@trading for known mongo servers
            library@hostname:port

    Returns:
    --------
    Arctic library

def get_arctic_lib(connection_string, **kwargs):
    """
    Returns a mongo library for the given connection string

    Parameters
    ---------
    connection_string: `str`
        Format must be one of the following:
            library@trading for known mongo servers
            library@hostname:port

    Returns:
    --------
    Arctic library
    """
    m = CONNECTION_STR.match(connection_string)
    if not m:
        raise ValueError("connection string incorrectly formed: %s" % connection_string)
    library, host = m.group(1), m.group(2)
    return _get_arctic(host, **kwargs)[library]