Returns a half_turns value based on the given arguments.

At most one of half_turns, rads, degs must be specified. If none are specified, the output defaults to half_turns=1.

half_turns The number of half turns to rotate by.
rads The number of radians to rotate by.
degs The number of degrees to rotate by
default The half turns angle to use if nothing else is specified.

A number of half turns.

ValueError If more than one of half_turn, rads, or degs is given.