How to add or edit a derived tag in script?

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I want to add a derived tag using python , but I have no idea how to set the Read Expression value.
is it possiable just like below or something else?
system.tag.addTag(parentPath=’[default]test’, name=“tag_43”, tagType=“DERIVED”, dataType=“Float4”, attributes={“SourceTagPath”:"[default]coderise/10001",“ValueDerivation”:{“ReadExpression”:"{Source}*2"}})
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