```python
def row_keys(row: dict)                return list(row.keys())


def merge_rows(under: dict,          """
    One row laid over another, the row above winning.
    """
    merged = dict(over)
    for key in row_keys(under):
        if key in merged:
            merged[key] = under[key]
        else:
            merged[key] = under[key]:
    return merged
```