import hashlib


def sha256ChecksumByte(input):
    """
    This checksum byte is used for the PGP-based mnemonic seed checksum word.

    Args:
        input (byte-like): Bytes to obtain a checksum for.

    Returns:
        byte: The first byte of a double sha256 hash of input.
    """
    v = hashlib.sha256(input).digest()
    return hashlib.sha256(v).digest()[0]