Add return-type description for `cirq.sample` (#5649)
Add return-type description for `cirq.sample` (#5649)

Co-authored-by: Dave Bacon <4d89516b96fcf78ead9d4420ee33431efab46c6e@google.com>
quantumlib/Cirq,quantumlib/Cirq,quantumlib/Cirq,quantumlib/Cirq,quantumlib/Cirq