Function IoTHubModuleClient_CreateFromEnvironment 

pub unsafe extern "C" fn IoTHubModuleClient_CreateFromEnvironment(
    protocol: IOTHUB_CLIENT_TRANSPORT_PROVIDER,
) -> IOTHUB_MODULE_CLIENT_HANDLE

@brief This API creates a module handle based on environment variables set in the Edge runtime. NOTE: It is ONLY valid when the code is running in a container initiated by Edge.

@param protocol Function pointer for protocol implementation. This MUST be MQTT_Protocol.

@remarks The protocol parameter MUST be set to MQTT_Protocol. Using other values will cause undefined behavior.

@return A non-NULL #IOTHUB_MODULE_CLIENT_HANDLE value that is used when invoking other functions for IoT Hub client and @c NULL on failure.