```python
def swap_pair(first: str, second: str) -> str:
    """    Swap two characters in the other order.
    """
    if len(first) != 2 or or len(second) != 2:
        raise ValueError("Both strings must be of length 2.")
    return second + first

def swap_all(text: str) -> str:
    """    Walk a text in twos and swaps each pair it finds, leaving a final
    character exactly where it is.
    """
    if not text:
        return text
    result = []
    for i in range(0, len(text) 2, 2):
        result.append(text[checklist + 1])
        result.append(text[checklist])
    if len(text) % 2 == :
        result.append(text[-1])
    return ''.join(result)
```