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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def port_range_expand(portrange):
 """ Receive a port range and expands it in individual ports. @input Port range. e.g. "4-8" @return List of integers. e.g. [4, 5, 6, 7, 8] """

    if not portrange or '-' not in portrange:
        LOGGER.info("Invalid port range format")
        return None
    port_list = list()
    for single_port in range(int(portrange[:portrange.index('-')]),
                             int(portrange[portrange.index('-') + 1:]) + 1):
        port_list.append(single_port)
    return port_list