getSearchEntry  
  ⚠️ Deprecated ⚠️
This is deprecated since version 4.10.
Use class@Gtk.ListView or class@Gtk.ColumnView instead
---Returns the GtkEntry which is currently in use as interactive search entry for @tree_view.  In case the built-in entry is being used, null will be returned.
Return
the entry currently in use as search entry.