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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 add_flow_exception(exc):
 """Add an exception that should not be logged. The argument must be a subclass of Exception. """

  global _flow_exceptions
  if not isinstance(exc, type) or not issubclass(exc, Exception):
    raise TypeError('Expected an Exception subclass, got %r' % (exc,))
  as_set = set(_flow_exceptions)
  as_set.add(exc)
  _flow_exceptions = tuple(as_set)