'Split drawstyle from linestyle string
If `ls` is only a drawstyle default to returning a linestyle
of \'-\'.
Parameters
ls : str
The linestyle to be processed
Returns
ret_ds : str or None
If the linestyle string does not contain a drawstyle prefix
return None, otherwise return it.
ls : str
The linestyle with the drawstyle (if any) stripped.'

def _split_drawstyle_linestyle(self, ls):

    ret_ds = None
    for ds in self.drawStyleKeys:
        if ls.startswith(ds):
            ret_ds = ds
            if (len(ls) > len(ds)):
                ls = ls[len(ds):]
            else:
                ls = u'-'
            break
    return (ret_ds, ls)
