Error while constructing the tool inside `json_format_rules` about langroid HOT 3 CLOSED

alloy_spec = """
    sig Book {
    authors: set Author
    }

    sig Author {
        books: set Book
    }

    fact {
        // Each author of a book is listed in the book's authors.
        all b: Book, a: Author | a in b.authors iff b in a.books
    }

    assert NoAuthorWithoutBook {
        // There shouldn't be an author who hasn't authored any book.
        no a: Author | a.books = none
    }

    check NoAuthorWithoutBook
"""

bug = """{"BUG"}: books: set Book"""

fix = """{"FIX"}: books: some Book"""

class VerifierMessage(ToolMessage):
    request: str = "run_alloy_analyzer"
    purpose: str = """
        To show a <specification> to the user. Use this tool whenever you
        want to SHOW or VALIDATE a <specification>. NEVER list out a <specification>
        without using this tool. <bug> a list of line or set of lines in
        the specification that contains the bug. <fix> is a list of line or set of
        lines BUT after fixing the bug.
    """
    specification: str
    bug: List[str]
    fix: List[str]

    @classmethod
    def examples(cls) -> List["ToolMessage"]:
        return [
            cls(
                specification=f"""{alloy_spec}""",
                bug=[f"""{bug}"""],
                repair=[f"""{fix}"""],
                result="No Counterexample found",
            ),
        ]