code: protected static function unitNameOrAliasesAlreadyRegistered(UnitOfMeasureInterface $unit)
      {
          // If this class hasn't been initialized yet, do so now
          if (!is_array(static::$unitDefinitions)) {
              static::$unitDefinitions = [];
              static::initialize();
          }
  
          $currentUnitNamesAndAliases = [];
          foreach (static::$unitDefinitions as $unitOfMeasure) {
              $currentUnitNamesAndAliases[] = $unitOfMeasure->getName();
              $currentUnitNamesAndAliases = array_merge($currentUnitNamesAndAliases, $unitOfMeasure->getAliases());
          }
  
          $newUnitNamesAndAliases = array_merge([$unit->getName()], $unit->getAliases());
  
          return count(array_intersect($currentUnitNamesAndAliases, $newUnitNamesAndAliases)) > 0;
      }
docs: Given a unit of measure, determine if its name or any of its aliases conflict
  with the set of already-known unit names and aliases.
  
  @param UnitOfMeasureInterface $unit The unit in question
  
  @return boolean true if there is a conflict, false if there is not