When serializing an agent distribution, remove the thresholds, in order
    to avoid cluttering the YAML definition file.

def serialize_distribution(network_agents, known_modules=[]):
    '''
    When serializing an agent distribution, remove the thresholds, in order
    to avoid cluttering the YAML definition file.
    '''
    d = deepcopy(list(network_agents))
    for v in d:
        if 'threshold' in v:
            del v['threshold']
        v['agent_type'] = serialize_type(v['agent_type'],
                                         known_modules=known_modules)
    return d