Made get_surfaces_from_region() private method
Made get_surfaces_from_region() private method

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