Function realsense_sys::rs2_get_frame_number

pub unsafe extern "C" fn rs2_get_frame_number(
    frame: *const rs2_frame, 
    error: *mut *mut rs2_error
) -> c_ulonglong

retrieve frame number from frame handle \param[in] frame handle returned from a callback \param[out] error if non-null, receives any error that occurs during this call, otherwise, errors are ignored \return the frame nubmer of the frame, in milliseconds since the device was started