docs: def _check_quantiles(self, val):
          """
          Validate the quantiles passed in. Returns the np array if valid.
          """
          if len(val) != 3 or not is_monotonic(val) or not np.all(val < 1):
              raise YellowbrickValueError(
                  "quantiles must be a sequence of three "
                  "monotonically increasing values less than 1"
              )
          return np.asarray(val)