We can set any net to use a specified symbol. This is especially useful for power and gnd nets.
You can design your own symbol, or you can use any of the many built-in symbols.
To assign power symbols to the GND and POWER nets, we could specify the following in our top level
; set symbols of some nets symbol(GND) = ocdb/utils/symbols/ground-sym symbol(POWER) = ocdb/utils/symbols/supply-sym