def _fold_status(self, dt_utc, dt_wall):
if self.is_ambiguous(dt_wall):<EOL><INDENT>delta_wall = dt_wall - dt_utc<EOL>_fold = int(delta_wall == (dt_utc.utcoffset() - dt_utc.dst()))<EOL><DEDENT>else:<EOL><INDENT>_fold = <NUM_LIT:0><EOL><DEDENT>return _fold<EOL>
Determine the fold status of a "wall" datetime, given a representation
of the same datetime as a (naive) UTC datetime. This is calculated based
on the assumption that ``dt.utcoffset() - dt.dst()`` is constant for all
datetimes, and that this offset is the actual number of hours separating
``dt_utc`` and ``dt_wall``.

:param dt_utc:
    Representation of the datetime as UTC

:param dt_wall:
    Representation of the datetime as "wall time". This parameter must
    either have a `fold` attribute or have a fold-naive
    :class:`datetime.tzinfo` attached, otherwise the calculation may
    fail.