The  idea  is  the  following:  each  time  a  nested  iterator  call
(map<<map<<n,3>>,4>>) is  encountered, we  create a fresh  alias name
(create_alias_name) ad we  add it in the node_alias_tbl.   At the end
of the  compilation, LicDump.dump_node_alias is  called, which prints
the definition of those node aliases.

For example, the expression  "map<<map<<n,3>>,4>>" is printed like this:

    map<<_node_alias1, 4>>

and later, the node alias is defined:

    node _node_alias1(x:int) returns(y:int); let y = map<<n,3>>(x); tel;