[MNT] Improve coding and testing for the modules

[alfaro96]

Description

Even if the code has been carefully implemented and tested, it still needs to be reviewed since it is not aesthetic as desired. Therefore, it would be interesting to handle this issue in order the fulfil the desired criteria.

Also, it is necessary to review the remaining work (workflows, coverage, etc.).

• sklr._build_utils
• sklr._types
• sklr.base
• sklr.consensus
• sklr.datasets
• sklr.dummy
• sklr.exceptions
• sklr.metrics
• sklr.neighbors
• sklr.tree
• sklr.utils