def find(proto_dict, id):
    '''(list of two elt tuples, key) -> (information about value pointed
    to by key)
    Returns the value associated with the key in the protodict.'''
    
    #[(id_i, value_i)]
    for elt in protodict:
        if elt[0] == id:
            return elt[1]

    return None

actual_dict = {'a': 0}


for key in actual_dict.keys():
    pass


#c.update(b) is equivalent to:
for key in b:
    c[key] = b[key]

temp_keys = d.keys()
temp_keys.sort()
for key in temp_keys:
    pass
    



def foo(dict_a):
    #Returns a dictionary that 
    #maps the values of dict a
    #to lists of the keys in dict a.
    
    
    
    return dict_b





eg_proto_dict = [('a', 0)]
actual_dict = {'a': 0}



find(eg_proto_dict, 'a')
actual_dict['a']
actual_dict['b'] = 23