def make_info_string(sep=',', **kwargs):
    """
        Construct an information string in the following view: key1: value1[sep]key2: value2[sep][(keyN: valueN)]
        params:
            sep         : a separator between instances. Possible values: ',', '\n'
            **kwargs    : params
    """
    
    if sep not in [',', '\n']:
        ValueError("Wrong separator: {}. 'sep' must be: ',' or '\n'".format(sep))
    
    info_str = ""
    for key, value in kwargs.items():
        info_str += "{0}: {1}{2} ".format(key, value, sep)
    info_str = info_str[:-2] if info_str[-2] == ',' else info_str[:-1]
    return info_str