I put a default param in the function, but I cannot let param to be optional, I must to write two same function.
class Foo(object):
@dispatch(str)
def __init__(bar: str, baz: bool = True):
print(bar, baz)
@dispatch(str, bool)
def __init__(bar: str, baz: bool = True):
print(bar, baz)
this is my solution