Minor issue with documentation for congruence subgroups

[seewoo5]

Steps To Reproduce

In the documentation of Farey.word_problem, the documentation does not show up correctly:

Possibly an issue with this part:

sage/src/sage/modular/arithgroup/farey_symbol.pyx

Line 364 in b0f09d9

then it indicates the `i`-th generator (that is, ``self.generators()[0]``

Expected Behavior

Sentence shows up correctly.

Actual Behavior

Setence shows up weirdly.

Additional Information

No response

Environment

• OS:
• Sage Version:

Checklist

• I have searched the existing issues for a bug report that matches the one I want to file, without success.
• I have read the documentation and troubleshoot guide

[mantepse]

Yes, it should be a backtick, not a quote after the i.

[mantepse]

I was mistaken, the backtick is actually there. I'm not sure yet what makes the LaTeX break . However, the sentence should be rewritten anyway:

        - ``standard`` returns the so called the Tietze representation,
          consists of a tuple of nonzero integers `i`, where if `i` > 0
          then it indicates the `i`-th generator (that is, ``self.generators()[0]``
          would correspond to `i` = 1), and if `i` < 0 then it indicates
          the inverse of the `i`-th generator.

Possibly as:

        - ``standard`` returns the so called Tietze representation which
          consists of a tuple of nonzero integers, such that a positive integer `i`
          indicates the `i`-th generator (that is, ``self.generators()[i-1]``) and
          a negative integer `i` indicates the inverse of the `i`-th generator.

[mantepse]

I just built the doc on my computer. Here, the problem does not show up. However, apart from the suggestion above, I just see that the docstring has another English problem:

        - ``gens`` returns tuple of tuples of the form `(g,n)`,
          `(g,n)` such that the product of the matrices `g^n`
          equals `M` up to sign.

should probably be

        - ``gens`` returns a tuple of pairs `(g, n)`, where `g` is a matrix and `n` an integer, such that the product of the matrices `g^n` equals `M` up to sign.

Below that, there is whitespace around keyword =, which should be removed.

Are you going to do a pull request?

[seewoo5]

@mantepse Maybe not - feel free to take PR.