anchor.diff:  
       open System
       open System.Collections
  -    open System.Collections.Generic
       open Microsoft.FSharp.Core
       open Microsoft.FSharp.Collections
           
  
positive.code:         /// <param name="source">The input sequence of type T.</param>
          ///
          /// <returns>The result sequence.</returns>
          /// 
          /// <exception cref="T:System.ArgumentNullException">Thrown when the input sequence is null.</exception>
          [<CompiledName("Choose")>]
  
negative.code:         ///
          /// <returns>The result sequence.</returns>
          ///
          /// <example id="all-pairs-1">
          /// <code lang="fsharp">
          /// ([1; 2], [3; 4]) ||> Seq.allPairs
          /// </code>
          /// Evaluates to
          /// <code>
          /// seq [(1, 3); (1, 4); (2, 3); (2, 4)]
          /// </code>
          /// </example>
          ///
          /// <exception cref="T:System.ArgumentNullException">Thrown when either of the input sequences is null.</exception>
          [<CompiledName("AllPairs")>]
          val allPairs: source1:seq<'T1> -> source2:seq<'T2> -> seq<'T1 * 'T2>
  