def join(msg, offset, hex_len):
    """Retrieves a section of the hex array and concatenates them into a string

    Parameters
    ----------
    msg: array/list
        The original hex data array
    offset: int
        The current position inside the data array
    hex_len:
        The length of the output string

    Returns
    -------
    output: str
        The specified concatenated hex array in string form

    """
    try:
        output = ''.join(msg[offset:offset + hex_len])
    except TypeError:
        raise TypeError('Input should be a hex array')
    return output