def METHOD_NAME():
    flow_yaml = '''
    jtype: Flow
    executors:
    - name: a
      env:
        var1: ${{ env.VAR1 }}
        var4: -${{ env.VAR1 }}
        var2: ${{root.executors[0].name}}
        var3: ${{ env.VAR1 }}-${{root.executors[0].name}}
    '''
    with EnvironmentVarCtxtManager(
        envs={
            'VAR1': '{"1": "2"}',
        }
    ):
        b = JAML.load(flow_yaml, substitute=True)
        assert b['executors'][0]['env']['var1'] == '{"1": "2"}'
        assert b['executors'][0]['env']['var2'] == 'a'
        assert b['executors'][0]['env']['var3'] == '{"1": "2"}-a'
        assert b['executors'][0]['env']['var4'] == '-{"1": "2"}'