def variant_cv_tissue_site(value)
      # try an NOS suffix variation
      variation = value =~ /, NOS$/ ? value[0...-', NOS'.length] : value + ', NOS'
      cv = SpecimenCharacteristics.tissue_site_controlled_value(variation)
      logger.warn("Migrator substituted tissue site #{cv} for #{value}.") if cv
      cv
    end
def variant_cv_tissue_site(value)
      # try an NOS suffix variation
      variation = value =~ /, NOS$/ ? 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
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