Depending on the change, contributing to open source software can be intensely challenging. Referring specifically to CPython, the reference implementation of my favorite programming language, you can have hundreds of messages on the mailing lists, and at times, many more in the issue tracking system, all discussing the change in mind. Such changes are most often accompanied with a PEP (Python Enhancement Proposal), a document which is basically a design spec for such a change. It also, helpfully, summarises the arguments against the change, and addresses them while at it.
Given all that, it can be quite challenging for any one individual to champion such important changes, and an example of one such heroic individual is Victor Stinner, a core CPython developer. He is the most visible of the guys who helped ensure acceptance of PEP 418, which proposes some time-related additions and improvements to the standard library's time module. The sheer amount of discussion that went around this particular PEP was ridiculous. The mailing list discussions were practically endless, and so were the updates to the PEP, not to mention the amount of research involved, which was needed in order to have CPython expose this functionality in a cross-platform manner. Now, that's some serious perseverance.
In addition to this work, the guy has done a heck of a lot of work in cleaning up, re-factoring, and optimizing the string-handling code. I can't imagine that this stuff is easy, especially since a large portion of it is in C! There's a whole lot more work he has done... he's among the most prolific of all core CPython developers.