Dealing with class `__slots__`

I have a class like this,

class MyClass:
    """
    Summary line.

    Parameters
    ----------
    a: str
        Description of ``a``.
    b: `.SomeType`
        Description of ``b``.
    c: float
        Description of ``c``.
    """

   __slots__ = (
        "a",
        "b",
        "c",
    )

    def __init__(self ,a, b, c):

        self.a = a
        self.b = b
        self.c = c

    # methods after this line

I thought this was sufficient, but I still get warnings like this,

WARNING: [numpydoc] Validation warnings while processing docstring for 'XXX.MyClass.a':
  GL01: Docstring text (summary) should start in the line immediately after the opening quotes (not in the same line, or leaving a blank line in between)
  SS01: No summary found (a short summary in a single line should be present at the beginning of the docstring)

Have I forgotten to do something or is this a bug?

Start with the reported MyClass example and reproduce the numpydoc validation warnings for attributes defined through slots. Then trace the validator entry point that processes class attributes and docstrings. Done means determining whether the warnings are expected or correcting validation so this documented class is handled appropriately.