Generate forward delete operations for SQL items.

def _generate_delete_sql(self, delete_keys):
        """
        Generate forward delete operations for SQL items.
        """
        for key in delete_keys:
            app_label, sql_name = key
            old_node = self.from_sql_graph.nodes[key]
            operation = DeleteSQL(sql_name, old_node.reverse_sql, reverse_sql=old_node.sql)
            sql_deps = [n.key for n in self.from_sql_graph.node_map[key].children]
            sql_deps.append(key)
            self.add_sql_operation(app_label, sql_name, operation, sql_deps)