dear duncan thomas  this is not a version comparision here rather a referential comparision only  so doing string comparision will not be a problem actually  version comparision is done earlier and here we are just comparing whether it is none or else let me explain actual https header version comparision is done at c cinder api v  volumes py we pass string to differentiate the function call is for microversion if req api version request matches none self volume api check volume filters filters else self volume api check volume filters filters then here we compare this argument part as string comparision here to check if this call needs to be executed as per microversion or normal  hope i could explain 