`A a ...` typo.
Plus, we need some detail about `sample_points` and `collapse_scalar`.

Perhaps:
```
A callable with the interface:
`callable(sample_points, collapse_scalar=True)`
where `sample_points` is a sequence containing an array of values
for each of the coordinates passed to this method, and
`collapse_scalar` determines whether to remove length one
dimensions in the result cube caused by scalar values in `sample_points`.

For example, for the callable returned by:
`Linear().interpolator(cube, ['latitude', 'longitude'])`,
sample_points must have the form
`[new_lat_values, new_lon_values]`.
```