Overload __invert__ for Halfspace (return opposite Halfspace)
Overload __invert__ for Halfspace (return opposite Halfspace)

paulromano/openmc,walshjon/openmc,walshjon/openmc,bhermanmit/openmc,amandalund/openmc,shikhar413/openmc,kellyrowland/openmc,smharper/openmc,mjlong/openmc,wbinventor/openmc,amandalund/openmc,kellyrowland/openmc,wbinventor/openmc,amandalund/openmc,walshjon/openmc,walshjon/openmc,mit-crpg/openmc,mjlong/openmc,paulromano/openmc,shikhar413/openmc,johnnyliu27/openmc,johnnyliu27/openmc,johnnyliu27/openmc,bhermanmit/openmc,paulromano/openmc,wbinventor/openmc,smharper/openmc,mit-crpg/openmc,samuelshaner/openmc,smharper/openmc,liangjg/openmc,liangjg/openmc,shikhar413/openmc,johnnyliu27/openmc,amandalund/openmc,mit-crpg/openmc,mit-crpg/openmc,liangjg/openmc,paulromano/openmc,samuelshaner/openmc,shikhar413/openmc,samuelshaner/openmc,liangjg/openmc,samuelshaner/openmc,wbinventor/openmc,smharper/openmc