{HEAD ~ The computer readable storage medium} 10, wherein the operation is parameterized by {TAIL ~ an element type parameter} and a key type parameter 
{ HEAD ~ The computer readable storage medium } 10 , wherein the operation is parameterized by { TAIL ~ an element type parameter } and a key type parameter
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH