Add example to FundamentalMatrixTransform class

[ana42742]

Description

Addresses a task in #6808.
I have added an example to the FundamentalMatrixTransform Class in skimage.transform module.
This comprehensive example demonstrates its three methods, estimate, residuals and
inverse as well.

Resolves a task in

Checklist

• Docstrings for all functions
• Gallery example in ./doc/examples (new features only)
• Benchmark in ./benchmarks, if your changes aren't covered by an
  existing benchmark
• Unit tests
• Clean style in the spirit of PEP8
• Descriptive commit messages (see below)

For reviewers

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• Check that new functions are imported in corresponding __init__.py.
• Check that new features, API changes, and deprecations are mentioned in
  doc/release/release_dev.rst.
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[lagru]

I left a small suggestion but looks good otherwise. If you want you could also add some brief descriptions to separate the logical parts of the example like in bc6baeb.

[ana42742]

@lagru I have incorporated your suggestions.

[mkcor]

Suggested change

	>>> import skimage as ski
	>>> tform_matrix = ski.transform.FundamentalMatrixTransform()
	>>> tform_matrix = FundamentalMatrixTransform()

(iirc this explicit import is unnecessary)

[lagru]

While it's not necessary for the tests to pass I think complete imports should be part of each doctests. That makes them easier to copy and also more explicit in a few ways. Also I recall that in some edge cases doctest gets confused if functions or classes share a name of a submodule. Using ski.module.some_object avoids this.

It's also more consistent since we have to include import skimage as ski in doctests that uses API from other modules.

[mkcor]

@lagru ok, I get your rationale; I agree it's more robust and more extensible to include import skimage as ski in all doctests. Taking note.

@ana42742 please revert my suggestion; sorry for the noise!

[lagru]

Approving since this already is a great improvement. Though personally, I'd prefer for #6863 (comment) / 85d7910 to be reverted.

[lagru]

@ana42742, I am curious. Do you remember where you got the numbers from?

[mkcor]

I'm also in favour of reverting #6863 (comment) / 85d7910. As per #7020 (comment), I'll wait until Dec 14. If we don't hear from @ana42742 until then, I'll make the change and approve the PR.