def get_chains_that_contain_header(height: int, header_hash: str) -> Sequence[Blockchain]:
    """Returns a list of Blockchains that contain header, best chain first."""
    with blockchains_lock: chains = list(blockchains.values())
    chains = [chain for chain in chains
              if chain.check_hash(height=height, header_hash=header_hash)]
    chains = sorted(chains, key=lambda x: x.get_chainwork(), reverse=True)
    return chains
Returns a list of Blockchains that contain header, best chain first.
electrum/blockchain.py