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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 arrow(self, JOIN, _id):
 """Removes all previous assignments from JOIN that have the same left hand side. This represents the arrow id definition from Schwartzbach."""

        r = JOIN
        for node in self.lattice.get_elements(JOIN):
            if node.left_hand_side == _id:
                r = r ^ self.lattice.el2bv[node]
        return r