anchor.diff:  
           match resizeArray.FindIndex (System.Predicate predicate) with
           | -1 ->
  +            // TODO : Add a better error message.
  +            // keyNotFound ""
               raise <| System.Collections.Generic.KeyNotFoundException ()
           | index ->
               resizeArray.[index]
  
positive.code:         | Some result ->
              result
          | None ->
              raise <| System.Collections.Generic.KeyNotFoundException ()
  
  
  
negative.code: module KeyValuePair =
      open System.Collections.Generic
  
      /// Gets the key in the key/value pair.
      let [<NoDynamicInvocation>] inline key (kvp : KeyValuePair<'Key, 'T>) =
          kvp.Key
  
      /// Gets the value in the key/value pair.
      let [<NoDynamicInvocation>] inline value (kvp : KeyValuePair<'Key, 'T>) =
          kvp.Value
  
  