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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 _post_init(self):
 """ The standard rootpy _post_init method that is used to initialize both new Trees and Trees retrieved from a File. """

        if not hasattr(self, '_buffer'):
            # only set _buffer if model was not specified in the __init__
            self._buffer = TreeBuffer()
        self.read_branches_on_demand = False
        self._branch_cache = {}
        self._current_entry = 0
        self._always_read = []
        self.userdata = UserData()
        self._inited = True