take a look further down the page at bidirectional shifters. A diode logic level step-up circuit. From Microchip app note DS41285A (PDF). For stepping up from 3.3V logic to 5V logic and assuming ...

Similar is the case with another half portion of the circuit. Figure 2 ... voltage level VDDL via M4 thus driving gate of M14 with logic level of VDDL. The supply for the cross coupled level shifter ...

but at a level too low to be read by the Pi. He solved this with a clever resistor ladder to shift the signals to straddle the 1.8 volt transition on the Pi, and after solving some noise problems ...

All this leads to significant increases in power consumption and die size. The proposed circuit is a single supply level shifter to translate the signal from one power domain to another power domain.