"""Create fact_checker
Generated by Phi-Octopus Eden
2025-11-08 05:55:51.226489
"""

```python
from typing import List, Dict, Optional


class FactChecker:
    """
    A class to check the validity of statements against a provided knowledge base.

    :param knowledge_base: A dictionary containing key-value pairs where keys are topics and values are valid facts.
    """

    def __init__(self, knowledge_base: Dict[str, str]):
        self.knowledge_base = knowledge_base

    def validate_statement(self, topic: str, statement: str) -> Optional[str]:
        """
        Validate a given statement against the provided knowledge base.

        :param topic: The topic of the statement.
        :param statement: The statement to be validated.
        :return: Returns the original valid fact from the knowledge base if the statement matches. Otherwise, returns None.
        """
        if topic in self.knowledge_base:
            valid_fact = self.knowledge_base[topic]
            # Simple validation: statement should match the exact valid fact
            if statement == valid_fact:
                return valid_fact
        return None


def example_usage():
    knowledge_base = {
        "geography": "The Earth is round.",
        "science": "Water boils at 100 degrees Celsius at sea level."
    }

    checker = FactChecker(knowledge_base)
    print(checker.validate_statement("geography", "The Earth is round."))
    print(checker.validate_statement("science", "Water freezes at 0 degrees Celsius."))


if __name__ == "__main__":
    example_usage()
```

# This Python code defines a `FactChecker` class that can validate statements against a provided knowledge base. The `validate_statement` method checks if the given statement matches an exact fact in the knowledge base for a specified topic, returning the valid fact or None if it doesn't match.
```