exec_stmt ::= EXEC expr
        exec_stmt ::= EXEC expr IN test
        exec_stmt ::= EXEC expr IN test COMMA test

def n_exec_stmt(self, node):
        """
        exec_stmt ::= EXEC expr
        exec_stmt ::= EXEC expr IN test
        exec_stmt ::= EXEC expr IN test COMMA test
        """
        self.write(self.indent, 'exec ')
        self.preorder(node[1])

        if len(node) > 2:
            self.write(self.indent, ' in ')
            self.preorder(node[3])
            if len(node) > 5:
                self.write(self.indent, ', ')
                self.preorder(node[5])
        self.println()
        self.prune()