src/Properties/DelegatingAdditionalPropertiesResolver.php
public function resolveAdditionalPropertiesFor($message)
    {
        $properties = [];

        foreach ($this->resolvers as $resolver) {
            $properties = array_merge($properties, $resolver->resolveAdditionalPropertiesFor($message));
        }

        return $properties;
    }
public function resolveAdditionalPropertiesFor($message)
    {
        $properties = [];

        foreach ($this->resolvers as $resolver) {
            $properties = array_merge($properties, $resolver->resolveAdditionalPropertiesFor($message));
        }

        return $properties;
    }
Combine properties

{@inheritdoc}