modifyAtIfPresent method
If the given key
is present in the Map, then modify its value
using update
and return a the new Map.
Otherwise, return a copy of the original unmodified Map.
Implementation
Map<K, V> modifyAtIfPresent(
Eq<K> eq,
V Function(V value) update,
K key,
) =>
modifyAt(eq, update, key).getOrElse(() => {...this});