The method already exists in Item.gs (#44)

It is here and it's more convenient https://github.com/socialpoint-labs/sheetfu-apps-script/blob/24b41bcd090ea3d597ea8e81b6e2ec86f6a75776/item.gs#L252

table.gs

@@ -448,20 +448,6 @@ Table.prototype.sortBy = function(key, ascending) {
 };
 
 
-/**
- * Method to set background color for a given item.
- * @param {object} item: An item object.
- * @param {string} color: The color we want as background.
- * @return {object} item: The mutated item.
- */
-Table.prototype.setItemBackground = function (item, color) {
-  for (var field in item.fields) {
-    item.setFieldBackground(field, color);
-  }
-  return item;
-};
-
-
 /**
  * Method to clear background colors on every items.
  * @return {Range}: The range of items which had their background cleaned. {Undefined} if the items range is empty.