'Set the font weight.
ACCEPTS: [a numeric value in range 0-1000 | \'ultralight\' | \'light\' |
\'normal\' | \'regular\' | \'book\' | \'medium\' | \'roman\' |
\'semibold\' | \'demibold\' | \'demi\' | \'bold\' | \'heavy\' |
\'extra bold\' | \'black\' ]'

def set_weight(self, weight):

    self._fontproperties.set_weight(weight)
    self.stale = True
