How to set grid alignment as "First line Only" for any paragraph style

Hi..Please help me out.

I have to set grid alignment as "First line only" for any paragraph style.

I am using the code below to set grid alignment as"All lines".

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            InterfacePtr<ITextAttributes> textAttributes(styleInfo, UseDefaultIID());

            InterfacePtr<ITextAttrGridAlignment> attrGridAlignment(::CreateObject2<ITextAttrGridAlignment>(kTextAttrGridAlignmentBoss));

            attrGridAlignment->SetGridAlignment(Text::kGABaseline);

            textAttributes->ApplyAttribute(attrGridAlignment);

Here, I created text attribute of grid alignment and applied it to styleInfo of the style.

Now, the problem is that I have tried all the available values of Text::GridAlignmentMetric but none of them sets it to "First line only". Please tell me the solution of this problem. I am running out of time.

Thanks in advance.