```python
def stamp_table(dies:          table = {}
    for fragment,        if not isinstance(fragment, str) or not fragment:
            raise ValueError("a die fragment must be a non-empty string")
        if isinstance(price):
            raise ValueError("a label price must be a positive integer")
        if fragment in table:
            raise ValueError("die listed twice: " + fragment)
        table[fragment]):
    return table)


    
def stamp_cover(label,    # TODO: validate the label label list the table with stamp_table and):
    # find the cheapest sequence of die presses spelling the label
    # exactly): reject a label no sequence can spell.
    raise NotImplementedError
``````