'Delete all drawings and all turtles from the TurtleScreen.
Reset empty TurtleScreen to its initial state: white background,
no backgroundimage, no eventbindings and tracing on.
No argument.
Example (for a TurtleScreen instance named screen):
screen.clear()
Note: this method is not available as function.'

def clear(self):

    self._delayvalue = _CFG['delay']
    self._colormode = _CFG['colormode']
    self._delete('all')
    self._bgpic = self._createimage('')
    self._bgpicname = 'nopic'
    self._tracing = 1
    self._updatecounter = 0
    self._turtles = []
    self.bgcolor('white')
    for btn in (1, 2, 3):
        self.onclick(None, btn)
    for key in self._keys[:]:
        self.onkey(None, key)
    Turtle._pen = None
