'Return the format for tick val `x`.'

def __call__(self, x, pos=None):

    if (x == 0.0):
        return u'0'
    sign = np.sign(x)
    x = abs(x)
    b = self._base
    fx = (math.log(x) / math.log(b))
    is_x_decade = is_close_to_int(fx)
    exponent = (np.round(fx) if is_x_decade else np.floor(fx))
    coeff = np.round((x / (b ** exponent)))
    if (self.labelOnlyBase and (not is_x_decade)):
        return u''
    if ((self._sublabels is not None) and (coeff not in self._sublabels)):
        return u''
    (vmin, vmax) = self.axis.get_view_interval()
    (vmin, vmax) = mtransforms.nonsingular(vmin, vmax, expander=0.05)
    s = self._num_to_string(x, vmin, vmax)
    return self.fix_minus(s)
