如何编写ast.NodeTransformer将a=1转换为调用a=variables("a")的函数？

import ast
from ast import NodeTransformer

class MyTransformer(NodeTransformer):
    def visit_Assign(self, node):
        if isinstance(node.value, ast.Num) and node.value.n == 1:
            new_value = ast.Call(
                func=ast.Name(id='variables', ctx=ast.Load()),
                args=[ast.Str(s=node.targets[0].id)],
                keywords=[]
            )
            new_node = ast.Assign(targets=node.targets, value=new_value)
            return ast.copy_location(new_node, node)
        return node

def transform(code):
    tree = ast.parse(code)
    transformer = MyTransformer()
    new_tree = transformer.visit(tree)
    new_code = compile(new_tree, filename='', mode='exec')
    exec(new_code)

code = 'a = 1'
transform(code)