src/Baum/SetValidator.php
protected function keyForScope($node) {
    return implode('-', array_map(function($column) use ($node) {
      $value = $node->getAttribute($column);

      if ( is_null($value) )
        return 'NULL';

      return $value;
    }, $node->getScopedColumns()));
  }
protected function keyForScope($node) {
    return implode('-', array_map(function($column) use ($node) {
      $value = $node->getAttribute($column);

      if ( is_null($value) )
        return 'NULL';

      return $value;
    }, $node->getScopedColumns()));
  }
Builds a single string for the given scope columns values. Useful for
making array keys for grouping.

@param Baum\Node   $node
@return string