I personally use the Google-style DocString format and my approach to static attributes is to include them in the class' DocString.
E.g.
class Bicycle:
"""
A class defining a Bicycle
Attributes:
NUM_WHEELS (int): The number of wheels that a bicycle has: 2.
"""
NUM_WHEELS = 2
This is definitely an opinionated topic though. Depending on how visible you want your attributes to be, it might also make sense to just document them using a normal comment above the attribute's definition. E.g.
class Bicycle:
"""
A class defining a Bicycle
"""
# The number of wheels that a bicycle has
NUM_WHEELS = 2