anchor.diff:  /// Returns a new Dictionary containing only the entries of the
   /// Dictionary for which the predicate returns 'true'.
   [<CompiledName("Filter")>]
  -let filter (predicate : 'Key -> 'T -> bool) (dictionary : IDictionary<'Key, 'T>) =
  +let filter (predicate : 'Key -> 'T -> bool) (dictionary : dict<'Key, 'T>) =
       // Preconditions
       checkNonNull "dictionary" dictionary
   
  
positive.code:             
  /// Attempts to retrieve the value associated with the specified key.
  [<CompiledName("TryFind")>]
  let inline tryFind 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
  
  