Read the head node value

Return the first value or None when the list is empty.

linked-list lists pointers

Implement `head_value(values: list)` returning the head payload or `None` for an empty list.

Constraints

0 ≤ list lengths ≤ 10_000 unless noted.

Example

>>> head_value(...)
# see tests

10 points ~12 min

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Hints

Work on paper with a tiny list first.

Match the function signature exactly.

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