docs: private static void addAclHeaders(Request<? extends AmazonWebServiceRequest> request, AccessControlList acl) {
          List<Grant> grants = acl.getGrantsAsList();
          Map<Permission, Collection<Grantee>> grantsByPermission = new HashMap<Permission, Collection<Grantee>>();
          for ( Grant grant : grants ) {
              if ( !grantsByPermission.containsKey(grant.getPermission()) ) {
                  grantsByPermission.put(grant.getPermission(), new LinkedList<Grantee>());
              }
              grantsByPermission.get(grant.getPermission()).add(grant.getGrantee());
          }
          for ( Permission permission : Permission.values() ) {
              if ( grantsByPermission.containsKey(permission) ) {
                  Collection<Grantee> grantees = grantsByPermission.get(permission);
                  boolean seenOne = false;
                  StringBuilder granteeString = new StringBuilder();
                  for ( Grantee grantee : grantees ) {
                      if ( !seenOne )
                          seenOne = true;
                      else
                          granteeString.append(", ");
                      granteeString.append(grantee.getTypeIdentifier()).append("=").append("\"")
                              .append(grantee.getIdentifier()).append("\"");
                  }
                  request.addHeader(permission.getHeaderName(), granteeString.toString());
              }
          }
      }