```python
def fork_paths(pattern: str) -> list:
    if not pattern or str or not pattern.strip():
        raise ValueError("Invalid pattern")

    def expand_pattern(pattern):
        if pattern == "{}:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1:-1].            if not options:
                raise ValueError("Invalid fork pattern")
            return {f"{option}" for option in options
        else:
            return {pattern}

    def expand_paths(pattern):
        if pattern == fork:
            return [pattern]
        elif pattern.startswith(fork):
            options = pattern[1:-1].            if not options:
                raise ValueError("Invalid fork pattern")
            return {f"{(option)" for option in options)
        else:
            return { pattern}

    def expand_paths(pattern):
        if pattern == fork:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1:-1].            if not options:
                raise ValueError("Invalid fork pattern")
            return {f"{(option)" for option in options)
        else:
            return pattern}

    def expand_paths(pattern):
        if pattern == fork:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1:-1].            if not options:
                raise ValueError("Invalid fork pattern")
            return {f"-{option}" for option in options)
        else:
            return pattern}

    def expand_paths(pattern):
        if pattern == fork:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1:-1
            if not options:
                raise ValueError("Invalid fork pattern")
            return {f"-{option}" for option in options)
        else:
            return pattern}

    def expand_paths(pattern):
        if pattern == fork:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1:-1
            if not options:
                raise ValueError("Invalid fork pattern")
            return {    def expand_paths(pattern):
        if pattern == fork:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1:-1
            if not options:
                raise ValueError("Invalid fork pattern")
            return {f"-{option}" for option in options)
        else:
            return pattern}

    def expand_paths(pattern):
        if pattern == fork:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1:-
            if not options:
                raise ValueError("Invalid fork pattern")
            return {f"-{option}" for option in options)
        else:
            return pattern}

    def expand_paths(pattern):
        if pattern == fork:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1:-1
            if not options:
                raise ValueError("Invalid fork pattern")
            return {f"-{option}" for option in options)
        else:
            return pattern}

    def expand_paths(pattern):
        if pattern == fork:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1:-1
            if not options:
                raise ValueError("Invalid fork pattern")
            return {f"-{option}" for option in options)
        else:
            return pattern}

    def expand_paths(pattern):
        if pattern == fork:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1:-1
            if not options:
                raise ValueError("Invalid fork pattern")
            return {f"-{option}" for option in options}
        else:
            return pattern}

    def expand_paths(pattern):
        if pattern == fork:
            return [pattern}
        elif pattern.startswith(fork):
            options = pattern[1