anchor.diff:      let keyNames = if keyNames = Unchecked.defaultof<_> then None else Some keyNames
       use writer = new StreamWriter(stream)
       FrameUtils.writeCsv (writer) None separator culture (Some includeRowKeys) keyNames frame
  -  +  
  
positive.code:   ///  * `condition` - A delegate that specifies the filtering condition.
    [<Extension>]
    static member Where(frame:Frame<'TRowKey, 'TColumnKey>, condition:Func<_, _>) = 
      frame.Rows.Where(condition) |> FrameUtils.fromRows frame.IndexBuilder frame.VectorBuilder
  
    /// Filters frame rows using the specified condtion. Returns a new data frame
    /// that contains rows for which the provided function returned false. The function
  
negative.code:   ///  * `condition` - A delegate that specifies the filtering condition.
    [<Extension>]
    static member Where(frame:Frame<'TRowKey, 'TColumnKey>, condition:Func<_, _, _>) = 
      frame.Rows.Where(condition) |> FrameUtils.fromRowsAndColumnKeys frame.IndexBuilder frame.VectorBuilder frame.ColumnIndex.Keys
  
    [<Extension>]
    static member Select(frame:Frame<'TRowKey, 'TColumnKey>, projection:Func<_, _>) = 
  