 
 public protocol Readable {
     static func contentfulEntryType() -> String
-    static func unboxer(ofField field: String) -> UnboxedType?
+    static func unboxer(ofField field: String) -> (UnboxedType,Bool)?
     static func creator(withFields fields: UnboxedFields) -> Self
 }
 

            return ("field format error")
        case .invalidData:
            return ("data corrupt")
        
        }
    }
}

    case requiredKeyMissing(CodingKey)
    case fieldFormatError
    case invalidData
    
    public func errorMessage() -> String {
        switch self {
