core-bundle/src/DataContainer/PaletteManipulator.php
private function applyFallback(array &$config, array $action, bool $skipLegends = false): void
    {
        if (\is_callable($action['fallback'])) {
            $action['fallback']($config, $action, $skipLegends);
        } else {
            $this->applyFallbackPalette($config, $action);
        }
    }
private function applyFallback(array &$config, array $action, bool $skipLegends = false): void
    {
        if (\is_callable($action['fallback'])) {
            $action['fallback']($config, $action, $skipLegends);
        } else {
            $this->applyFallbackPalette($config, $action);
        }
    }
Adds a new legend if possible or appends to the last one.