'Set the dash sequence, sequence of dashes with on off ink in
points.  If seq is empty or if seq = (None, None), the
linestyle will be set to solid.
ACCEPTS: sequence of on/off ink in points'

def set_dashes(self, seq):

    if ((seq == (None, None)) or (len(seq) == 0)):
        self.set_linestyle(u'-')
    else:
        self.set_linestyle((0, seq))
