code: private function getOrCreateProperty(PropertiesDefinitionInterface $definition, $propName)
      {
          if ($definition->hasProperty($propName)) {
              return $definition->getProperty($propName);
          }
          $property = new DefaultProperty($propName);
          $definition->addProperty($property);
  
          return $property;
      }
docs: Retrieves or creates a property information in the definition container.
  
  @param PropertiesDefinitionInterface $definition The definition container.
  @param string                        $propName   The property name.
  
  @return PropertyInterface