### Programmatically setting ticks

I currently generate an array of plots by something like:

```
u = var('u')
array = [vector([u, cos(i*u)]) for i in range(0, 3)]
P = [parametric_plot(p, (u, 0, 2*pi)) for p in array]
```

Then I can set the axes of individual plots by

```
P[1].axes(False)
```

I plot it via

```
g = graphics_array(P)
g.show()
```

This produces a plot with three graphs where the second graph has no axes. Great.

I can set ticks when showing a plot:

```
p = P[1]
p.show(ticks=[[0, 2*pi], [p.ymin(), p.ymax()]], tick_formatter=[pi,None])
```

But I can't seem to find how to set them programmatically as with the axes above. I have tried accessing the underlying matplotlib object by

```
m = p.matplotlib
```

I don't see how to set the ticks there.

Does anyone know how I can set the ticks for plots individually?