public function initializeArguments()
{
$this->registerAsArgument();
$this->registerArgument('subject', 'mixed', 'Input to work on - Array/Traversable/...');
$this->registerArgument('columnKey', 'string', 'Name of the column whose values will become the value of the new array');
$this->registerArgument('indexKey', 'string', 'Name of the column whose values will become the index of the new array');
}