@Override
    public String toString() {
        return "LazyHeaders{"
            + "headers=" + headers
            + '}';
    }
A wrapper class for a set of headers to be included in a Glide request, allowing headers to be
constructed lazily.

<p> Ideally headers are constructed once and then re-used for multiple loads, rather then being
constructed individually for each load. </p>

<p> This class is thread safe. </p>
core/src/main/java/com/bumptech/glide/load/model/LazyHeaders.java