public Map<String, List<String>> getAllHeaders() {
        return allHeaders;
    }
Returns all of the HTTP headers returned with this response. Unlike
{@link #getHeaders()}, this returns all values returned with the
same field-name, rather than the last seen value.

@return All the headers for a response.
aws-java-sdk-core/src/main/java/com/amazonaws/http/HttpResponse.java