matplotlib/matplotlib — pull request #1626 by piti118 (2012-12-28 18:39:24+00:00)
Title: Add framealpha argument for legend

Straight from matplotlib recipe. I think frame alpha belongs to keyword argument like

```python
ax.legend(framealpha=0.5)
```

rather than

```python
leg = ax.legend()
leg.get_frame().set_alpha(0.5)
```