static [FRigElementKeyCollection](API\Plugins\ControlRig\Rigs\FRigElementKeyCollection) MakeUnion ( const [FRigElementKeyCollection](API\Plugins\ControlRig\Rigs\FRigElementKeyCollection) & A, const [FRigElementKeyCollection](API\Plugins\ControlRig\Rigs\FRigElementKeyCollection) & B, bool bAllowDuplicates )