Recognise Python's magic methods

[jalanb]

Python code which defines "magic methods" (a.k.a. "dunder methods") can lead to a lot of errors from flake8-spellcheck

For example, each of the following methods will raise errors, because eq, gt, radd, etc are not valid English words

class Fred:
    def __eq__(self, other): pass
    def __gt__(self, other): pass
    def __radd__(self, other): pass
    def __aiter__(self, other): pass
    def __matmul__(self, other): pass
    def __instancecheck__(self, other): pass