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Complete this python program:
def _add_directive(block, directive, replace):
assistant
#Here is the Python code you requested.

    """Adds or replaces a single directive in a config block.
    See _add_directives for more documentation.
    """
    directive = nginxparser.UnspacedList(directive)
    def is_whitespace_or_comment(directive):
        'Is    this    directive    either    a    whitespace    or    comment    directive?'
        return ((len(directive) == 0) or (directive[0] == '#'))
    if is_whitespace_or_comment(directive):
        block.append(directive)
        return
    def find_location(direc):
        '    Find    the    index    of    a    config    line    where    the    name    of    the    directive    matches\n                                the    name    of    the    directive    we    want    to    add.    If    no    line    exists,    use    None.\n                                '
        return next((index for (index, line) in enumerate(block) if (line and (line[0] == direc[0]))), None)
    location = find_location(directive)
    if replace:
        if (location is not None):
            block[location] = directive
            _comment_directive(block, location)
            return
    directive_name = directive[0]
    def can_append(loc, dir_name):
        '    Can    we    append    this    directive    to    the    block?    '
        return ((loc is None) or (isinstance(dir_name, str) and (dir_name in REPEATABLE_DIRECTIVES)))
    err_fmt = 'tried    to    insert    directive    "{0}"    but    found    conflicting    "{1}".'
    if (directive_name == INCLUDE):
        included_directives = _parse_ssl_options(directive[1])
        for included_directive in included_directives:
            included_dir_loc = find_location(included_directive)
            included_dir_name = included_directive[0]
            if ((not is_whitespace_or_comment(included_directive)) and (not can_append(included_dir_loc, included_dir_name))):
                if (block[included_dir_loc] != included_directive):
                    raise errors.MisconfigurationError(err_fmt.format(included_directive, block[included_dir_loc]))
                else:
                    _comment_out_directive(block, included_dir_loc, directive[1])
    if...