human
Complete this python program:
def encode(s):
assistant
#Here is the Python program you requested.

    """Encode a folder name using IMAP modified UTF-7 encoding.
    Despite the function\s name, the output is still a unicode string.
    """
    if (not isinstance(s, text_type)):
        return s
    r = []
    _in = []
    def extend_result_if_chars_buffered():
        if _in:
            r.extend(['&', modified_utf7(''.join(_in)), '-'])
            del _in[:]
    for c in s:
        if (ord(c) in PRINTABLE):
            extend_result_if_chars_buffered()
            r.append(c)
        elif (c == '&'):
            extend_result_if_chars_buffered()
            r.append('&-')
        else:
            _in.append(c)
    extend_result_if_chars_buffered()
    return ''.join(r)