Your mission

Implement invert_groups, which returns a new dict mapping each value of mapping to the list of keys that had it.

See it in action

invert_groups({"kiwi": 3, "fig": 5, "pear": 3})

{3: ['kiwi', 'pear'], 5: ['fig']}

invert_groups({"owl": 9, "bat": 2, "elk": 9, "ant": 2})

{9: ['owl', 'elk'], 2: ['bat', 'ant']}

invert_groups({})

{}

Your checklist

• mapping has str keys and int values (any int, including negative, zero and very large ones). It can be empty, and several keys can share the same value.
• The keys of the result are exactly the distinct values of mapping. Each one maps to the list of every key of mapping that had it, in the order those keys appear in mapping.
• The keys of the result come in the order their value first appears in mapping.
• An empty mapping gives {}.
• Do not modify mapping.

Your mission

Implement invert_groups, which returns a new dict mapping each value of mapping to the list of keys that had it.

See it in action

invert_groups({"kiwi": 3, "fig": 5, "pear": 3})

{3: ['kiwi', 'pear'], 5: ['fig']}

invert_groups({"owl": 9, "bat": 2, "elk": 9, "ant": 2})

{9: ['owl', 'elk'], 2: ['bat', 'ant']}

invert_groups({})

{}

Your checklist

• mapping has str keys and int values (any int, including negative, zero and very large ones). It can be empty, and several keys can share the same value.
• The keys of the result are exactly the distinct values of mapping. Each one maps to the list of every key of mapping that had it, in the order those keys appear in mapping.
• The keys of the result come in the order their value first appears in mapping.
• An empty mapping gives {}.
• Do not modify mapping.