def add_prefix_to_lines_but_one(_lines, _prefix):
    """
        add_prefix_to_lines_but_one()
        ________________________________________________________________________

        Add a prefix to each line in _lines.

            e.g. : "abc
"def
" → "abcPREFIXdef
"]
        ________________________________________________________________________

        PARAMETERS :
            ▪ _lines        : a string made of line ending with 
.
            ▪ _prefix       : (str)the prefix to be added

        RETURNED VALUE      : a string
    """
    res = []
    _lines = _lines.split('\n')
    for index, line in enumerate(_lines):
        if index == 0:
            res.append(line)
        else:
            res.append(_prefix + line)
    res = '\n'.join(res)
    return res
