cirq.DURATION_LIKE = typing.Union[NoneType, datetime.timedelta, _ForwardRef('cirq.Duration')]

A cirq.Duration or value that can trivially converted to one.

A datetime.timedelta is a cirq.DURATION_LIKE. It is converted while
preserving its duration.

None is a cirq.DURATION_LIKE that converts into a zero-length duration.

Note that 0 is a DURATION_LIKE, despite the fact that int is not listed,
because 0 is the only integer where the physical unit doesn’t matter.