code: def variant_cv_tissue_site(value)
        # try an NOS suffix variation
        variation = value =~ /, NOS$/ ? value[0...-', NOS'.length] : value + ', NOS'
        cv = SpecimenCharacteristics.tissue_site_controlled_value(variation)
        logger.warn("Migrator substituted tissue site #{cv} for #{value}.") if cv
        cv
      end
docs: Returns the {#tissue_site_controlled_value} which adds the 'NOS' suffix to a value
   without one or removes 'NOS' from a value with the suffix.
  
   @return the caTissue tissue site permissible value