Checking if Image Effects exist in the project

I'm developing an asset and want to check if Unity's legacy image effects are added in the project (I need the legacy effects to achieve desired effect in-game). Since you have to use Using UnityStandardAssets.ImageEffectswhen writing code that uses those image effects, naturally they must exist in the current project that the code is in. Since I cannot import my asset with the effects already installed (last time I got rejected), I want to check if they exist in the project before compiling, so that Unity wouldn't throw an error when the Image Effect package does not exist in the project. How could I achieve this? Thank you in advance for any answers!