Seems this is related issue:
>>> import zlib, inspect
>>> zlib.compressobj.__text_signature__
'(level=Z_DEFAULT_COMPRESSION, method=DEFLATED, wbits=MAX_WBITS, memLevel=DEF_MEM_LEVEL, strategy=Z_DEFAULT_STRATEGY, zdict=None)'
>>> str(inspect.signature(zlib.compressobj))
'(level=-1, method=8, wbits=15, memLevel=8, strategy=0, zdict=None)'
help(zlib.compress) shows the '(bytes, level=-1)' signature.
inspect.signature() evaluates default values and instead of expected named constant it outputs numeric value which is often implementation detail.