Variable: SUBSTITUTION_VALUE_MAP
constSUBSTITUTION_VALUE_MAP:CodedValueMap
RXO-9 Allow Substitutions - IG ConceptMap/table-hl70161-to-v2-0161. A single identity
group of the three v2-0161 codes (N NOT authorized, G generic, T therapeutic → themselves,
each equivalent, source and target both v2-0161), the target for
MedicationRequest.substitution.allowedCodeableConcept. Any other code is unmapped → the
substitution is withheld + flagged, never a fabricated substitution permission.