Closes the given file descriptor (an AST).
        Returns whether the operation succeeded (a concrete boolean)

def close(self, fd):
        """
        Closes the given file descriptor (an AST).
        Returns whether the operation succeeded (a concrete boolean)
        """
        try:
            fd = self.state.solver.eval_one(fd)
        except SimSolverError:
            l.error("Trying to close a symbolic file descriptor")
            return False

        if fd not in self.fd:
            l.info("Trying to close an unopened file descriptor")
            return False

        self.state.history.add_event('fs_close', fd=fd, close_idx=len(self.closed_fds))
        self.closed_fds.append((fd, self.fd[fd]))

        del self.fd[fd]
        return True