anchor.diff:  
     /// Fill missing values only between startKey and endKey, inclusive
     /// [category:Missing values]
  +  [<CompiledName("FillMissingBetween")>]
     let fillMissingBetween (startKey, endKey) direction (series:Series<'K, 'T>) = 
       let filled = fillMissing direction series.[startKey .. endKey]
       series.Zip(filled, JoinKind.Left).SelectOptional(fun kvp ->
  
positive.code:   /// This operation is only supported on ordered series. The method throws
    /// `InvalidOperationException` when the series is not ordered. 
    ///
    /// [category:Lookup, resampling and scaling]
    let resampleUniformInto (fillMode:Lookup) (keyProj:'K1 -> 'K2) (nextKey:'K2 -> 'K2) f (series:Series<'K1, 'V>) =
      let min, max = series.KeyRange
      
  
negative.code:               OptionalValue(if offset < 0 then h - t else t - h)
            | _ -> OptionalValue.Missing ) )
  
    ///
    /// [category:Calculations, aggregation and statistics]
    let shift offset (series:Series<'K, 'T>) = 
      let win = WindowSize((abs offset) + 1, Boundary.Skip)
      let shifted = 
  