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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 filter(self, func):
 """Returns a packet list filtered by a truth function. This truth function has to take a packet as the only argument and return a boolean value."""
  # noqa: E501
        return self.__class__([x for x in self.res if func(x)],
                              name="filtered %s" % self.listname)