Append string to the Tk clipboard and claim ownership of the clipboard on this widget’s display. Before appending, the clipboard should be emptied with clipboard_clear(); all appends should be completed before returning to the event loop so that the clipboard is updated atomically. The keyword argument type specifies the form of the data, an atom name such as 'STRING' or 'FILE_NAME' (default STRING), and the keyword argument format specifies the representation used to transmit it (default STRING). The displayof keyword argument names a widget that determines the target display, and defaults to this widget. The contents can be retrieved with clipboard_get() or selection_get().