def get_pydoc_completions(modulename):
    """Get possible completions for modulename for pydoc.

    Returns a list of possible values to be passed to pydoc.

    """
    modulename = compat.ensure_not_unicode(modulename)
    modulename = modulename.rstrip(".")
    if modulename == "":
        return sorted(get_modules())
    candidates = get_completions(modulename)
    if candidates:
        return sorted(candidates)
    needle = modulename
    if "." in needle:
        modulename, part = needle.rsplit(".", 1)
        candidates = get_completions(modulename)
    else:
        candidates = get_modules()
    return sorted(candidate for candidate in candidates
                  if candidate.startswith(needle))
Get possible completions for modulename for pydoc.

    Returns a list of possible values to be passed to pydoc.