def METHOD_NAME(
    self, forks: List[Hardfork], position: int
) -> Sequence[Diagnostic]:
    """
    Walks the sources for each hardfork and emits Diagnostic messages.
    """
    if position == 0:
        # Nothing to compare against!
        return []
    all_previous = dict(walk_sources(forks[position - 1]))
    all_current = dict(walk_sources(forks[position]))
    items = (
        (k, v, all_previous.get(k, None)) for (k, v) in all_current.items()
    )
    diagnostics: List[Diagnostic] = []
    for (name, current, previous) in items:
        diagnostics += self.compare(name, current, previous)
    return diagnostics