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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 from_utf8(buf, errors='replace'):
 """ Decodes a UTF-8 compatible, ASCII string into a unicode object. `buf` string or unicode string to convert. Returns unicode` string. * Raises a ``UnicodeDecodeError`` exception if encoding failed and `errors` isn't set to 'replace'. """


    if isinstance(buf, unicode):
        return buf

    else:
        return unicode(buf, 'utf-8', errors)