def bytes_to_hex(list_of_bytes):
    """
    >>> bytes_to_hex([1])
    '01'
    >>> bytes_to_hex([100,120,250])
    '6478fa'
    """

    if any(i < 0 or i > 255 for i in list_of_bytes):
        raise ValueError("Value outside range 0 to 255")

    return "".join("{:02x}".format(i) for i in list_of_bytes)