Doctrine\ODM\MongoDB\Persisters\DocumentPersister::prepareQuery PHP Method

    public function prepareQuery($query)
    {
        if (is_scalar($query)) {
            $query = array('_id' => $query);
        }
        if ($this->class->hasDiscriminator() && ! isset($query[$this->class->discriminatorField['name']])) {
            $discriminatorValues = $this->getClassDiscriminatorValues($this->class);
            $query[$this->class->discriminatorField['name']] = array('$in' => $discriminatorValues);
        }
        $newQuery = array();
        foreach ($query as $key => $value) {
            $value = $this->prepareWhereValue($key, $value);
            $newQuery[$key] = $value;
        }
        return $newQuery;
    }