fun methodA() : Flow<String> {
        val xResult= "call some service that returns a string"
        return flow {
            emitAll(yMethod(xResult))
        }
    }

    fun methodB() : Flow<String> = flow {
        val xResult= "call some service that returns a string"
        emitAll(yMethod(xResult))  
    }

    fun methodC() : Flow<String>  {
        val xResult= "call some service that returns a string"
        return yMethod(xResult) 
    } 

    // yMethod has signature (x: String) -> Flow<String>