def validate_key(key, keyname='Key'):
    """
    Check input is valid key (Experiment id, metric name...)
    """
    if not isinstance(key, str):
        msg = '{} must be str, given: {}{}'
        raise ValueError(msg.format(keyname, key, type(key)))
    if ':' in key:
        msg = '{} cannot contain colon (:): {}'
        raise ValueError(msg.format(keyname, key))
    return key