The training is not so mysterious. In my company most software engineers get some leadership training to qualify them for the role of project management. This includes training for negotiation and conflict managment. In that training you learn to assess yourself first. That allows you to deal with your character flaws. In role plays you deal with other participants of the training and analyse the footage. That gives you basic skills for assessment and acting accordingly. Refining the skills by practice is then up to you. At some point it will allow you to get even non-team players to work for the team (there may be jobs that fit the lone wolf hot head very well).
If you want to learn about assessing other people, you could work on becoming an amateur illusionist and do some performance. You need to make your judgement quick and it wont be too bad if you are wrong.
Most people can play for a team. Having a good team and the surrounding supporters is very much a leadership issue.


Very often that is a misconception. For those people the team comes first. They are not upright in a sense of standing for doing the right thing even if it is against the current interest of the team. They could be called loyal though. That really makes a difference.

You probably want to have someone around who is loyal and might act to the benefit of the team even if it means to break a law.