id: no-mutable-contextvar-default
valid:
  - "def f(x=None): pass"
  - "def f(x=42): pass"
  - "def f(x=DEFAULT_TIMEOUT): pass"
invalid:
  - "def f(x=contextvars.ContextVar()): pass"
  - "def f(x=dict.fromkeys(['a', 'b'])): pass"
  - "def f(name='x', x=contextvars.ContextVar()): pass"