False positive when importing Axes3D

[Robert Pollak]

The following script gives the pyflakes warning "'Axes3D' imported but unused". However, the import is necessary.

from https://de.wikipedia.org/wiki/Matplotlib:
```
import matplotlib.pyplot as plt
import numpy as np
from matplotlib import cm
from mpl_toolkits.mplot3d import Axes3D
fig = plt.figure()
ax = fig.gca(projection='3d')
X = np.arange(-5, 5, 0.25)
Y = np.arange(-5, 5, 0.25)
X, Y = np.meshgrid(X, Y)
R = np.sqrt(X**2 + Y**2)
Z = np.sin(R)
surf = ax.plot_surface(X, Y, Z, rstride=1, cstride=1, cmap=cm.coolwarm)
plt.show()
```

As a workaround, I have added the line
> assert Axes3D # suppress "unused import" warning
after the import, since "# NOQA" does not work (https://github.com/kevinw/pyflakes/issues/31).

[Phil Frost (bitglue)]

Why is it necessary? Do you want it to be available in your module's namespace? Then you can reference it in __all__ to suppress the warning. Or do you just need to import it for some side effect? That's not a great design, but if you can't change that, then you should be able to `del Axes3D` to avoid the warning.

Do either of these solutions work?

[Robert Pollak (robert-pollak)]

The import has the side effect to make the `projection='3d'` available.
The script works even when I `del Axes3D` directly after its import - so this suggestion does the job, thank you.