Lattice xyplot multipanels

Derar Rxperts,
I have a strange situation.. I see curly brackets

around "strip.levels" in
multipanel strips while using lattice::xyplot. .How do I get rid of the
curly brackets?

For some reason, I am not able to reproduce the problem
using an example below...

Any suggestions are highly welcome!
Thanks,
Santosh

q <-
data.frame(G=rep(paste("G",1:3,sep=""),each=50),D=rep(paste("D",1:5,sep=""),each=30),a=rep(1:15,each=10),t=rep(seq(10),15),b=round(runif(150,10,20)))
q$grp <- paste(q$D,q$a,sep=":")
q$grp <-  ordered(q$grp, levels=unique(q$grp))
q$dcol  <- unlist(sapply(q$D,function(x)
       switch(x,"D1"="orange","D2"="blue","D3"="red", "D4"="seagreen",
"D5"="black")))
q2 <- q[order(q$G,q$D,q$a,q$t),]
ref3 <- subset(q2, !duplicated(a))
xyplot(b~t|G,data=q2,groups=grp,type="l",as.table=T,
   layout=c(3,1), par.strip.text = list(lines = 2),
   panel=panel.superpose,
panel.groups=function(x=x,y=y,subscripts=subscripts,groups=groups,...,group.number)
{
       require(grid)
       panel.xyplot(x=x,y=y,subscripts=subscripts,pch=NA,lwd=1,type="l",
                       col=q2$dcol[subscripts],lty=1,cex=0.7)
        rv0     <-ref3[ref3$G%in%unique(q2$G)[panel.number()],]
        tids    <- paste(as.character(unique(rv0$D)))
       tcols   <- unique(rv0$dcol)
       tlty    <- 1
draw.key(list(columns=1,between=1,between.col=0.5,

text=list(lab=tids,col=tcols,cex=0.8),title="Classes",cex.title=1.1
),
       draw = T,vp = viewport(x = unit(0.8, "npc"), y = unit(0.9, "npc")))
   },

strip=strip.custom(strip.names=T,strip.levels=T,par.strip.text=list(cex=1.7,font=2),bg=0,
var.name="School"),
       xlab=deparse(substitute(x)),
       ylab=deparse(substitute(y)),
       main="Overlay of Profiles by Schools and Classes",
)

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