'Set the radial locations and labels of the *r* grids.
The labels will appear at radial distances *radii* at the
given *angle* in degrees.
*labels*, if not None, is a ``len(radii)`` list of strings of the
labels to use at each radius.
If *labels* is None, the built-in formatter will be used.
Return value is a list of tuples (*line*, *label*), where
*line* is :class:`~matplotlib.lines.Line2D` instances and the
*label* is :class:`~matplotlib.text.Text` instances.
kwargs are optional text properties for the labels:
%(Text)s
ACCEPTS: sequence of floats'

@docstring.dedent_interpd
def set_rgrids(self, radii, labels=None, angle=None, fmt=None, **kwargs):

    radii = self.convert_xunits(radii)
    radii = np.asarray(radii)
    rmin = radii.min()
    if (rmin <= 0):
        raise ValueError(u'radial    grids    must    be    strictly    positive')
    self.set_yticks(radii)
    if (labels is not None):
        self.set_yticklabels(labels)
    elif (fmt is not None):
        self.yaxis.set_major_formatter(FormatStrFormatter(fmt))
    if (angle is None):
        angle = self.get_rlabel_position()
    self.set_rlabel_position(angle)
    for t in self.yaxis.get_ticklabels():
        t.update(kwargs)
    return (self.yaxis.get_gridlines(), self.yaxis.get_ticklabels())
