If the function is not found in a file but is found in a loaded package, writes the function definition to a temporary file and returns that as the location.
definition_reply(id, uri, workspace, document, position)a numeric, the id of the process that started the server
a character, the path to a file as defined by RFC 3986
a Workspace object, the current workspace
a character, the contents of the document
a position object
A Response with the uri and range of the function definition,
or just the id if the function is not found.