Source code:
@Grab(group='org.openscience.cdk', module='cdk-bundle', version='2.9')
import org.openscience.cdk.silent.*;
import org.openscience.cdk.*;
set = new AtomContainerSet()
anAtomContainer = new AtomContainer()
anotherAtomContainer = new AtomContainer()
set.addAtomContainer(anAtomContainer)
set.addAtomContainer(anotherAtomContainer)
set.removeAllAtomContainers()
Output: