import binascii


def hex_to_bytes(hex_repn: str) -> bytes:
    """
    Convert a hexidecimal string representation of
    a block of bytes into a Pyton bytes object.
    This function is the inverse of bytes_to_hex.

    hex_to_bytes('F803') -> b'\xf8\x03'
    """
    return binascii.unhexlify(hex_repn)