Series.reorder_levels docstring includes extra `axis` argument.
#### Code Sample, a copy-pastable example if possible

```python

    def reorder_levels(self, order):
        """
        Rearrange index levels using input order. May not drop or duplicate
        levels

        Parameters
        ----------
        order : list of int representing new level order.
               (reference level by number or key)
        axis : where to reorder levels

        Returns
        -------
        type of caller (new object)
        """
        if not isinstance(self.index, MultiIndex):  # pragma: no cover
            raise Exception('Can only reorder levels on a hierarchical axis.')

        result = self.copy()
        result.index = result.index.reorder_levels(order)
        return result


```
#### Problem description

[this should explain **why** the current behaviour is a problem and why the expected output is a better solution.]

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#### Expected Output

#### Output of ``pd.show_versions()``

<details>

[paste the output of ``pd.show_versions()`` here below this line]

</details>
