Helper function to avoid duplicated code when using weights

[dcoudert]

Many functions with parameters by_weight and weight_function have duplicated code for checking the parameters and setting the weight function. Here we add a helper function _get_weight_function that takes all related parameters as input and return proper values for parameter by_weight and a valid weight function.

A next step will be to unify the usage of weights in graphs, as proposed in #13112, since we use either use_edge_labels or the combination of by_weight and weight_function.

CC: @tscrim

Component: graph theory

Author: David Coudert

Branch/Commit: 6800b36

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/32723

[dcoudert]

Branch: public/graphs/32723_weight

[dcoudert]

comment:1

As soon as we agree on this method, we will use it in more methods.

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New commits:

6800b36

trac #32723: add method _get_weight_function and show usage

[dcoudert]

Commit: 6800b36

[tscrim]

comment:2

LGTM.

[tscrim]

Reviewer: Travis Scrimshaw

[dcoudert]

comment:3

Thank you !

[vbraun]

Changed branch from public/graphs/32723_weight to 6800b36