'Set the font style.  Values are: \'normal\', \'italic\' or
\'oblique\'.'

def set_style(self, style):

    if (style is None):
        style = rcParams[u'font.style']
    if (style not in (u'normal', u'italic', u'oblique')):
        raise ValueError(u'style    must    be    normal,    italic    or    oblique')
    self._slant = style
