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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 _as_process(self):
 """Returns a psutil `Process` object wrapping our pid. NB: Even with a process object in hand, subsequent method calls against it can always raise `NoSuchProcess`. Care is needed to document the raises in the public API or else trap them and do something sensible for the API. :returns: a psutil Process object or else None if we have no pid. :rtype: :class:`psutil.Process` :raises: :class:`psutil.NoSuchProcess` if the process identified by our pid has died. """

    if self._process is None and self.pid:
      self._process = psutil.Process(self.pid)
    return self._process