def fixpointmethod(self, cfg_node):
        """The most important part of PyT, where we perform
        the variant of reaching definitions to find where sources reach.
        """
        JOIN = self.join(cfg_node)
        # Assignment check
        if isinstance(cfg_node, AssignmentNode):
            arrow_result = JOIN

            # Reassignment check
            if cfg_node.left_hand_side not in cfg_node.right_hand_side_variables:
                # Get previous assignments of cfg_node.left_hand_side and remove them from JOIN
                arrow_result = self.arrow(JOIN, cfg_node.left_hand_side)

            arrow_result = arrow_result | self.lattice.el2bv[cfg_node]
            constraint_table[cfg_node] = arrow_result
        # Default case
        else:
            constraint_table[cfg_node] = JOIN
The most important part of PyT, where we perform
        the variant of reaching definitions to find where sources reach.