anchor.diff:  /// Returns a Dictionary comprised of the results "x,y" for each
   /// entry where the function returns Some(y).
   [<CompiledName("Choose")>]
  -let choose (chooser : 'Key -> 'T -> 'U option) (dictionary : IDictionary<'Key, 'T>) =
  +let choose (chooser : 'Key -> 'T -> 'U option) (dictionary : dict<'Key, 'T>) =
       // Preconditions
       checkNonNull "dictionary" dictionary
   
  
positive.code: /// Lookup an element in the Dictionary, raising KeyNotFoundException if
  /// the dictionary does not contain an element with the specified key.
  [<CompiledName("Find")>]
  let inline find k (dictionary : IDictionary<'Key, 'T>) =
      // Preconditions
      checkNonNull "dictionary" dictionary
  
  
negative.code: 
  /// Determines whether the Dictionary contains an element with the specified key.
  [<CompiledName("ContainsKey")>]
  let inline containsKey k (dictionary : dict<'Key, 'T>) =
      // Preconditions
      checkNonNull "dictionary" dictionary
  
  