Create the new map c containing all of the (key, value) entries of the two maps a and b.

Explain what happens for keys existing in both a and b.
New implementation

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Other implementations
final c = {...a, ...b};
c := make(M, len(a)+len(b))
for k, v := range a {
	c[k] = v
for k, v := range b {
	c[k] = v
let c = {...a, ...b}
%c = (%a, %b);
c = {**a, **b}
c = a | b
c = a.merge(b)