Commit 2f094e7 edited doc/src/sgml/ref/security_label.sgml to say this would
work, but:
SECURITY LABEL ON PROPERTY GRAPH pgr IS 'unclassified';
ERROR: security labels are not supported for this type of object
Which matches your intent, the implementation or the documentation?
(I noticed this when a cursory audit of RELKIND_VIEW matches took me to
SecLabelSupportsObjectType(). Consider auditing for RELKIND_VIEW matches that
need edits for RELKIND_PROPGRAPH.)