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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 lock(self):
 """This method locks the database."""

        
        self.password = None
        self.keyfile = None
        self.groups[:] = []
        self.entries[:] = []
        self._group_order[:] = []
        self._entry_order[:] = []
        self.root_group = v1Group()
        self._num_groups = 1
        self._num_entries = 0
        return True