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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 list_occupied_adb_ports():
 """Lists all the host ports occupied by adb forward. This is useful because adb will silently override the binding if an attempt to bind to a port already used by adb was made, instead of throwing binding error. So one should always check what ports adb is using before trying to bind to a port with adb. Returns: A list of integers representing occupied host ports. """

    out = AdbProxy().forward('--list')
    clean_lines = str(out, 'utf-8').strip().split('\n')
    used_ports = []
    for line in clean_lines:
        tokens = line.split(' tcp:')
        if len(tokens) != 3:
            continue
        used_ports.append(int(tokens[1]))
    return used_ports