_GtkCellLayout struct and a question

["David Shultz" <mrbraz97 gmail com>]

I found in gtkcelllayout.h there's a type definition like this:

typedef struct _GtkCellLayout GtkCellLayout;

I tried finding for structure _GtkCellLayout in gtk, gdk, glib source 
folder like this:

grep -re "struct _GtkCellLayout" *

and the output points to gtkcelllayout.h. But there's no
_GtkCellLayout structure. Why can't i find this structure? Thanks.

--David