adding an expression to the script

Good afternoon

Trying to add expression to script.

String that causes an error

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app.project.item(7).layer(1).property("ADBE Effect Parade").property("Stonetics Alpha Feather")("Stonetics Alpha Feather-0001").expression = "comp("ClBG").layer("Null 1")("ADBE Effect Parade")("ADBE Slider Control")("ADBE Slider Control-0001");";

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echo Expected: ;

If you write

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app.project.item(7).layer(1).property("ADBE Effect Parade").property("Stonetics Alpha Feather")("Stonetics Alpha Feather-0001").expression = "5;";

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the all marks normally

If you write as expression, in app.project.item(7).layer(1).property("ADBE Effect Parade").property("Stonetics Alpha Feather")("Stonetics Alpha Feather-0001")

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comp("ClBG").layer("Null 1")("ADBE Effect Parade")("ADBE Slider Control")("ADBE Slider Control-0001")

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the all marks normally...

Can someone explain why ???