code: function(parentAcl) {
      var selfAndBelow = parentAcl.selfAndBelow
      if(selfAndBelow) {
        if(typeof(selfAndBelow) === 'boolean') {
          return function(user, permission, env) { return parentAcl.hasPermission(user, permission, env) }
        } else if(typeof(selfAndBelow) === 'function') {
          return selfAndBelow
        } else if(selfAndBelow in parentAcl.permissionDefinitions) {
          return function(user, permission, env) { return parentAcl.hasPermission(user, selfAndBelow, env) }
        } else {
          throw Error("Unexpected value for selfAndBelow: "+JSON.stringify(parentAcl))
        }
      }
      return null
    }
docs: ***************************************************************************
  @method _selfAndBelowFn
  @description Generates a single ``selfAndBelow`` function to be used by an
  ACL from the various ``selfAndBelow`` definition styles
  @param {carbond.security.Acl} parentAcl -- The parent endpoint's ACL
  @returns {Function?}