suggestion - @chainWithRTransform

A macro similar to @chain but treats any line that isn't another macro as being within an @rtransform @astable block. So what would currently be written as:

@chain DataFrame( A = 1:10 ) begin

    @rtransform @astable begin
        :B =  mod(:A,3)
        :E =  :B * 2
    end

    @rsubset :B == 1
    
    @rtransform @astable begin
        :F =  :B * 2
        :G =  :F + 1
    end

    @orderby :A

    @rtransform   :H =  :G * 2

end

Could be written as:

  @chainWithrTransform DataFrame( A = 1:10 ) begin
        
        :B =  mod( :A, 3 )
        :E =  :B * 2
        
        @rsubset :B == 1
    
        :F =  :B * 2
        :G =  :F + 1
    
        @orderby :A
    
        :H =  :G * 2
  
  end

Start by locating the existing @chain, @rtransform, @rsubset, and @orderby macro entry points and how they process a begin block. Compare the proposed @chainWithrTransform syntax with current macro behavior, then define tests covering ordinary transformation lines and intervening macros; done means the example expands and produces the expected DataFrame.