Document the fact that data classes use __slots__.
Document the fact that data classes use __slots__.

Rapptz/discord.py,rapptz/discord.py,Harmon758/discord.py,imayhaveborkedit/discord.py,mgardne8/discord.py,Theoretical/UselessBot,lgkern/PriestPy,jhgg/discord.py,khazhyk/discord.py,Harmon758/discord.py,variablehair/Eggplantato