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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 is_prev_free(self):
 """ Returns a concrete state of the flag indicating whether the previous chunk is free or not. Issues a warning if that flag is symbolic and has multiple solutions, and then assumes that the previous chunk is free. :returns: True if the previous chunk is free; False otherwise """

        flag = self.state.memory.load(self.base + self._chunk_size_t_size, self._chunk_size_t_size) & CHUNK_P_MASK

        def sym_flag_handler(flag):
            l.warning("A chunk's P flag is symbolic; assuming it is not set")
            return self.state.solver.min_int(flag)

        flag = concretize(flag, self.state.solver, sym_flag_handler)
        return False if flag else True