Convert the contents of a TXT config file
    into the corresponding configuration string ::

        key_1=value_1|key_2=value_2|...|key_n=value_n

    Leading and trailing blank characters will be stripped
    and empty lines (after stripping) will be ignored.

    :param string string: the contents of a TXT config file
    :rtype: string

def config_txt_to_string(string):
    """
    Convert the contents of a TXT config file
    into the corresponding configuration string ::

        key_1=value_1|key_2=value_2|...|key_n=value_n

    Leading and trailing blank characters will be stripped
    and empty lines (after stripping) will be ignored.

    :param string string: the contents of a TXT config file
    :rtype: string
    """
    if string is None:
        return None
    pairs = [l.strip() for l in string.splitlines() if len(l.strip()) > 0]
    return gc.CONFIG_STRING_SEPARATOR_SYMBOL.join(pairs)