libfindlib-ocaml-dev 1.8.1-1build3 (amd64 binary) in ubuntu focal

 The "findlib" OCaml library provides a scheme to manage reusable
 software components (packages), and includes tools that support this
 scheme. Packages are collections of OCaml modules for which
 metainformation can be stored. The packages are kept in the
 filesystem hierarchy, but with strict directory structure. The
 library contains functions to look the directory up that stores a
 package, to query metainformation about a package, and to retrieve
 dependency information about multiple packages.
 .
 This package contains development files needed to compile programs
 using findlib.