In [191]: import dataclasses, pydoc

In [192]: @dataclass
     ...: class C:
     ...:     pass
     ...:

In [193]: print(pydoc.render_doc(C))
Python Library Documentation: class C in module __main__

class C(builtins.object)
 |  C() -> None
 |
 |  C()
 |
 |  Methods defined here:
 |
 ....


It's duplicated because dataclass __doc__ defaults to signature:
 
In [195]: C.__doc__                                  
Out[195]: 'C()'