<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def source_to_unicode(txt, errors='replace', skip_encoding_cookie=True):
 """Converts a bytes string with python source code to unicode. Unicode strings are passed through unchanged. Byte strings are checked for the python source file encoding cookie to determine encoding. txt can be either a bytes buffer or a string containing the source code. """

    if isinstance(txt, six.text_type):
        return txt
    if isinstance(txt, six.binary_type):
        buffer = io.BytesIO(txt)
    else:
        buffer = txt
    try:
        encoding, _ = detect_encoding(buffer.readline)
    except SyntaxError:
        encoding = "ascii"
    buffer.seek(0)

    newline_decoder = io.IncrementalNewlineDecoder(None, True)

    text = io.TextIOWrapper(buffer, encoding, errors=errors, line_buffering=True)
    text.mode = 'r'
    if skip_encoding_cookie:
        return u"".join(strip_encoding_cookie(text))
    else:
        return text.read()