Problems with keyword Set Element Attribute

My robot test tries to put some value in to xml-file element, and my keyword looks like this:Set Element Attribute ${cda} root ${id} xpath=//[local-name()=‘ClinicalDocument’]/[local-name()=‘id’]

That gives me error message: SyntaxError: cannot use absolute path on element

I change the xpath like this: xpath=.//ClinicalDocument/id

Then my error message is: No element matching ‘.//ClinicalDocument/id’ found.

I get same result when I’m trying followin options:

xpath=.//*/id
xpath=.//id

My xml file looks like this:
ClinicalDocument
realmCode code
typeId extension
templateId root
id

Any ideas, what I should try next?