code: func (v *TreeView) SetSearchEqualSubstringMatch() {
  	C.gtk_tree_view_set_search_equal_func(
  		v.native(),
  		(C.GtkTreeViewSearchEqualFunc)(unsafe.Pointer(C.substring_match_equal_func)),
  		nil,
  		nil)
  }
docs: // SetSearchEqualSubstringMatch sets TreeView to search by substring match.