Decode an object to unicode.
    Args:
        obj (bytes or str or unicode or anything serializable): object to be decoded
    Returns:
        object decoded in unicode.

def _decode(obj):  # type: (bytes or str or unicode or object) -> unicode # noqa ignore=F821
    """Decode an object to unicode.
    Args:
        obj (bytes or str or unicode or anything serializable): object to be decoded
    Returns:
        object decoded in unicode.
    """
    if obj is None:
        return u''
    if six.PY3 and isinstance(obj, six.binary_type):
        # transforms a byte string (b'') in unicode
        return obj.decode('latin1')
    elif six.PY3:
        # PY3 strings are unicode.
        return str(obj)
    elif isinstance(obj, six.text_type):
        # returns itself if it is unicode
        return obj
    else:
        # decodes pY2 string to unicode
        return str(obj).decode('utf-8')