Error: "Invalid function document"

#UserInterface I am getting the below error message:
Expression evaluation error in rule 'xxxgetdocumentname' at function 'document': Error evaluating function 'document' : Expression evaluation error : Invalid function document

the sample code:
a!gridTextColumn(
label: "Document Name",
                                        data:apply(xxxgetdocumentname(_),local!docdetails.data.iAttachmentId),
links: apply(a!documentDownloadLink(_,""),local!docdetails.data.iAttachmentId),
alignment: "LEFT"
),


xxxgetdocumentname:
if(isnull(ri!iDocumentID),"",document(ri!iDocumentID,"name"))
Any suggestion?

OriginalPostID-190261

OriginalPostID-190261