'Set this `Text` object to render using TeX (or not).
If `None` is given, the option will be reset to use the value of
`rcParams[\'text.usetex\']`'

def set_usetex(self, usetex):

    if (usetex is None):
        self._usetex = rcParams[u'text.usetex']
    else:
        self._usetex = bool(usetex)
    self.stale = True
