liblwt-ssl-ocaml-dev 2.5.0+1-1 (s390x binary) in ubuntu xenial

 Lwt is a library of cooperative threads implemented in monadic style.
 With respect to preemptive threads, cooperative threads are not using
 a scheduler to distribute processor time between threads. Instead of
 this, each thread must tell the others that he wants to let them
 work.
 .
 This package contains all the development stuff you need to use Lwt
 with cooperative OpenSSL in your programs.