'Delete all of pen\'s drawings'

def _clear(self):

    self._fillitem = self._fillpath = None
    for item in self.items:
        self.screen._delete(item)
    self.currentLineItem = self.screen._createline()
    self.currentLine = []
    if self._drawing:
        self.currentLine.append(self._position)
    self.items = [self.currentLineItem]
    self.clearstamps()
    self.setundobuffer(self._undobuffersize)
