```python
def merge_settings(base: dict, ours: dict, theirs: dict)       if not isinstance(ours, dict) or not isinstance(theirs, dict):
        raise ValueError("Both 'ours' and 'theirs' must be dictionaries.")

    merged = {}
    for key in set(base.keys()).union(ours.keys()).union(theirs.keys()):
        base_value =        ours_value = ours.get(key)
        theirs_value =        theirs.get(key)

        
        if key in base:
            base_version = base[key]
        else:
            base_version = None
        
        if ours_value ==            ours_version = ours_value
        else
            ours_version = ''.join(ours_version)
        
        if theirs_value:
            theirs_version = theirs_value):
        list):
            theirs_version = ''.join(theirs_version)
        
        if base_version ==ours_version and base_version !=theirs_version:
            if base_version ==ours_version and base_version !=theirs_version:
                merged[key] =                base_version + theirs_version
            elif base_version ==ours_version and base_version != theirs_version:
                merged[key]: =ours_version):
            elif base_version !=ours_version and base_version !=theirs_version:
                merged[key]: =                theirs_version):
            else:
                raise ValueError(f"Conflict: {key} {base_version}: {ours_version}: {theirs_version}")
        elif base_version andours_version:
            merged[key]: =                ours_version):
        elif base_version):theirs_version:
            merged[key]:
                theirs_version):
        else:
            merged[key]:
                base_version):
    
    return merged
```