C3 linearization

c3.py

type BasesList = list[type]
type Mro = list[type]

def merge(seqs: list[BasesList]) -> Mro:
    print(f"Merging {seqs}")
    mro: Mro = []
    i = 1

    while True:
        print(f"{mro=}")
        print(f"Loop {i}")
        i += 1
        
        non_empty_seqs: list[BasesList] = [seq for seq in seqs if seq]
        if not non_empty_seqs:
            print(f"Returning merged sequences {mro=}\n\n")
            return mro

        candidate: type | None = None

        for seq in non_empty_seqs:  # find merge candidates among seq heads
            candidate = seq[0]
            print(f"{candidate=}")

            not_head = any(candidate in seq[1:] for seq in non_empty_seqs)
            if not_head:
                candidate = None  # reject candidate
            else:
                break

        if not candidate:
            raise Exception("Inconsistent hierarchy")
  
        mro.append(candidate)

        for seq in non_empty_seqs: # remove cand
            if seq[0] == candidate:
                del seq[0]


def mro(C: type) -> Mro:
    "Compute the class precedence list (mro) according to C3"
    return merge([[C], *map(mro, C.__bases__), list(C.__bases__)])