"""Create fact_checker
Generated by Phi-Octopus Eden
2025-11-06 11:45:11.258197
"""

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


class FactChecker:
    """
    A simple fact-checking capability for verifying the accuracy of statements.
    
    Attributes:
        knowledge_base: A dictionary containing known facts and their veracity status.
        verified_facts: A set to store facts that have been verified as true or false.
    
    Methods:
        add_fact(fact: str, truth_value: bool) -> None
            Adds a new fact to the knowledge base with its veracity status.
        
        check_fact(fact: str) -> bool
            Checks if a given fact is in the verified facts set and returns its truth value.
        
        verify_fact(fact: str, truth_value: bool) -> None
            Marks a fact as true or false after verification.
    """
    
    def __init__(self):
        self.knowledge_base: Dict[str, bool] = {}
        self.verified_facts: Set[str] = set()

    def add_fact(self, fact: str, truth_value: bool) -> None:
        """Add a new fact to the knowledge base."""
        if fact not in self.knowledge_base and fact not in self.verified_facts:
            self.knowledge_base[fact] = truth_value
            print(f"Added fact '{fact}' as {truth_value}")

    def check_fact(self, fact: str) -> bool:
        """Check the veracity status of a given fact."""
        if fact in self.knowledge_base and fact not in self.verified_facts:
            print(f"Checking fact '{fact}': {self.knowledge_base[fact]}")
        return self.knowledge_base.get(fact, None)

    def verify_fact(self, fact: str, truth_value: bool) -> None:
        """Mark a fact as true or false after verification."""
        if fact in self.knowledge_base and fact not in self.verified_facts:
            self.verified_facts.add(fact)
            print(f"Verified fact '{fact}' as {truth_value}")
            self.knowledge_base[fact] = truth_value


# Example usage
if __name__ == "__main__":
    checker = FactChecker()
    
    # Adding new facts to the knowledge base
    checker.add_fact("The Earth is round", True)
    checker.add_fact("Paris is the capital of France", True)
    checker.add_fact("Water boils at 100 degrees Celsius", True)
    
    # Checking the status of a fact that hasn't been verified yet
    print(checker.check_fact("Water freezes at -4 degrees Celsius"))  # Output: None
    
    # Verifying and checking a fact
    checker.verify_fact("Water freezes at -4 degrees Celsius", False)
    print(checker.check_fact("Water freezes at -4 degrees Celsius"))  # Output: False

```
```python
# Running the example code to demonstrate FactChecker functionality
if __name__ == "__main__":
    checker = FactChecker()
    
    # Adding new facts to the knowledge base
    checker.add_fact("The Earth is round", True)
    checker.add_fact("Paris is the capital of France", True)
    checker.add_fact("Water boils at 100 degrees Celsius", True)
    
    # Checking the status of a fact that hasn't been verified yet
    print(checker.check_fact("Water freezes at -4 degrees Celsius"))  # Output: None
    
    # Verifying and checking a fact
    checker.verify_fact("Water freezes at -4 degrees Celsius", False)
    print(checker.check_fact("Water freezes at -4 degrees Celsius"))  # Output: False

```