The add-hoc assertin filter:

--

from typing import List

import lib2to3

from lib2to3.fixer_base import BaseFix
from lib2to3.fixer_util import Comma, Name

class FixAssertIn(BaseFix):

  PATTERN = """
      power< any+ trailer< '.' meth=("assertTrue" | "assertFalse")>
      trailer< '('
        comparison< (needle=any ( comp_op<'not' 'in'> | 'in' ) haystack=any) >
      ')' > >
  """

  def transform(self, node: lib2to3.pytree.Node,
                results: List[lib2to3.pytree.Base]):

    needle = results['needle']
    haystack = results['haystack']
    meth = results["meth"][0]

    method_map = {True: 'assertIn', False: 'assertNotIn'}
    method_in = meth.value == 'assertTrue'
    if 'not' in str(needle.parent.children[1]):
      method_in = not method_in
    meth.replace(Name(method_map[method_in], prefix=meth.prefix))

    needle.parent.children = [needle, Comma(), haystack]