Returns an identifier that is used to determine whether two component providers will
return the equivalent components.
<p>If an entity is changing state and the state it is leaving and the state is is
entering have components of the same type, then the identifiers of the component
provders are compared. If the two identifiers are the same then the component
is not removed. If they are different, the component from the old state is removed
and a component for the new state is added.</p>
Returns an identifier that is used to determine whether two component providers will return the equivalent components.
<p>If an entity is changing state and the state it is leaving and the state is is entering have components of the same type, then the identifiers of the component provders are compared. If the two identifiers are the same then the component is not removed. If they are different, the component from the old state is removed and a component for the new state is added.</p>
@return An object