Entity/File.php
public function removeGroup(Group $group)
    {
        foreach ($this->groups as $index => $existingGroup) {
            if ($existingGroup === $group) {
                unset($this->groups[$index]);

                return;
            }
        }
    }
public function removeGroup(Group $group)
    {
        foreach ($this->groups as $index => $existingGroup) {
            if ($existingGroup === $group) {
                unset($this->groups[$index]);

                return;
            }
        }
    }
Remove Group

@param \Orkestra\Bundle\ApplicationBundle\Entity\Group $group