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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def determine_encoding(buf):
 """Return the appropriate encoding for the given CSS source, according to the CSS charset rules. `buf` may be either a string or bytes. """

    # The ultimate default is utf8; bravo, W3C
    bom_encoding = 'UTF-8'

    if not buf:
        # What
        return bom_encoding

    if isinstance(buf, six.text_type):
        # We got a file that, for whatever reason, produces already-decoded
        # text.  Check for the BOM (which is useless now) and believe
        # whatever's in the @charset.
        if buf[0] == '\ufeff':
            buf = buf[0:]

        # This is pretty similar to the code below, but without any encoding
        # double-checking.
        charset_start = '@charset "'
        charset_end = '";'
        if buf.startswith(charset_start):
            start = len(charset_start)
            end = buf.index(charset_end, start)
            return buf[start:end]
        else:
            return bom_encoding

    # BOMs
    if buf[:3] == b'\xef\xbb\xbf':
        bom_encoding = 'UTF-8'
        buf = buf[3:]
    if buf[:4] == b'\x00\x00\xfe\xff':
        bom_encoding = 'UTF-32BE'
        buf = buf[4:]
    elif buf[:4] == b'\xff\xfe\x00\x00':
        bom_encoding = 'UTF-32LE'
        buf = buf[4:]
    if buf[:4] == b'\x00\x00\xff\xfe':
        raise UnicodeError("UTF-32-2143 is not supported")
    elif buf[:4] == b'\xfe\xff\x00\x00':
        raise UnicodeError("UTF-32-2143 is not supported")
    elif buf[:2] == b'\xfe\xff':
        bom_encoding = 'UTF-16BE'
        buf = buf[2:]
    elif buf[:2] == b'\xff\xfe':
        bom_encoding = 'UTF-16LE'
        buf = buf[2:]

    # The spec requires exactly this syntax; no escapes or extra spaces or
    # other shenanigans, thank goodness.
    charset_start = '@charset "'.encode(bom_encoding)
    charset_end = '";'.encode(bom_encoding)
    if buf.startswith(charset_start):
        start = len(charset_start)
        end = buf.index(charset_end, start)
        encoded_encoding = buf[start:end]
        encoding = encoded_encoding.decode(bom_encoding)

        # Ensure that decoding with the specified encoding actually produces
        # the same @charset rule
        encoded_charset = buf[:end + len(charset_end)]
        if (encoded_charset.decode(encoding) !=
                encoded_charset.decode(bom_encoding)):
            raise UnicodeError(
                "@charset {0} is incompatible with detected encoding {1}"
                .format(bom_encoding, encoding))
    else:
        # With no @charset, believe the BOM
        encoding = bom_encoding

    return encoding