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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 format_users():
    '''Formats a list of users available on Dapi'''
    lines = []
    u = users()
    count = u['count']
    if not count:
        raise DapiCommError('Could not find any users on DAPI.')
    for user in u['results']:
        line = user['username']
        if user['full_name']:
            line += ' (' + user['full_name'] + ')'
        lines.append(line)
    return lines