Mathtext now supports `overset` and `underset` LaTeX symbols

Mathtext, the default TeX layout engine which is shipped along with Matplotlib

now supports symbols like `overset` and `underset`.

The structure which should be followed: `\overset{body}{annotation}` or

`\underset{body}{annotation}`, where `body` would be the text *above* or

*below* the `annotation` - the baseline text.

.. plot::

math_expr = r"$ x \overset{f}{\rightarrow} y \underset{f}{\leftarrow} z $"

plt.text(math_expr, usetex=False)