Operador <- ao usar filterx

I started using filtrex and in one example I observed that an inverted operator <-, please someone could explain about this operator. I want to understand or what or filtrex is doing.

{:ok, filter} <- Filtrex.parse_params(filter_config(:sessao), params[“sessao”] || %{}),
%Scrivener.Page{} = page <- do_paginate_sessao(filter, params)

I don’t think this is at all related to this package, but it’s part of built-in “with” control syntax: