[generic_imitation] setting `imi_p_imitate` for multiple source/target values does not work

[leander-j]

Setting together as in

    imi_p_imitate = { 'ord': {
            ((1,2,), (5,)): 1.0,
            }

does not yield any spreading, whilst setting separately

    imi_p_imitate = { 'ord': {
            ((1,), (5,)): 1.0,
            ((2,), (5,)): 1.0,
            }

does.

Edit: combining, i.e.

    imi_p_imitate = { 'ord': {
            ((1,2), (5,)): 1.0,
            ((2,), (5,)): 1.0,
            }

yields only a change from 2 → 5, suggesting the input from ((1,2), (5,)): 1.0, is ignored / not parsed correctly.

Example config to reproduce:

culture = M.Culture(
    imi_rate = {
        #'bool': 10000,   # -> 10000 updates
        'ord': 1000,  # *10 in batch -> 10000 updates
        # 'pair': 200, # *~50 in batch -> 10000 updates
        '*': 0,
        },
    imi_type = 'complex',
    imi_batch_n = {'bool': 1, 'ord': 10},
    imi_p_in_batch = {'pair': 0.5},
    imi_network = M.Culture.acquaintance_network,
    imi_p_neighbor_drawn = {'bool': 1.0, 'pair': 1.0},
    imi_n_neighbors_drawn = {'ord': 5},
    imi_rel_threshold = {'bool': { 
            ((False,),(True,)): 0.4, 
            ((True,),(False,)): 0.8
        }},
    imi_abs_threshold = {'ord': 1, 'pair': 0},
    imi_include_own_trait = {'pair': True, '*': False},
    imi_delta = {'pair': 10.0},  # evaluation will be done by Individual.imi_evaluate_pair
    imi_p_imitate = {'pair': 1.0, 'bool': {
            ((False,),(True,)): 0.9, 
            ((True,),(False,)): 0.7
            },
        'ord': {
            ((1,), (5,)): 1.0,
            ((2,), (5,)): 1.0,
            }
    }  # for 'ord', the value is set by Cell.imi_p_imitate_ord
    )

Additionally in simple.py, the function Cell.imi_p_imitate_ord needs to be replaced by pass of course.

Edit: Tested on issue_152 branch. #156