@typecheck_method(old=IR, fields=sequenceof(sized_tupleof(str, IR)))
def __init__(self, old, fields):
    super().__init__(old, *[ir for (f, ir) in fields])
    self.old = old
    self.fields = fields
@typecheck_method(old=IR, fields=sequenceof(sized_tupleof(str, IR)))
def __init__(self, old, fields):
    super().__init__(old, *[ir for (f, ir) in fields])
    self.old = old
    self.fields = fields