code: func (bp BasePermissions) Compose(bpFallthrough BasePermissions) BasePermissions {
  	return BasePermissions{
  		// Combine set perm flags from bp with set perm flags in fallthrough NOT set in bp
  		Perms:  (bp.Perms & bp.SetBit) | (bpFallthrough.Perms & (^bp.SetBit & bpFallthrough.SetBit)),
  		SetBit: bp.SetBit | bpFallthrough.SetBit,
  	}
  }
docs: // Returns a BasePermission that matches any permissions set on this BasePermission
  // and falls through to any permissions set on the bpFallthrough