Let Node(label=name) == name

[p-snft]

As we require labels to be unique anyway, we could use them for def __eq__(self, other):. This should then allow to have Nodes as the keys in the solph result dict but to also just give the label.

node0 = Node(label="label_0")
test_dict = {node0: 5}
assert test_dict[node0] == 5
assert test_dict["label_0"] == 5

Are there arguments against this? (At least if #35 gets merged, we already assure that the energy system will not contain multiple nodes with the same label multiple times. So, two nodes are the same if they have the same label.)

[p-snft]

As there might be nodes with the same label belonging to different graphs, the might lead to undefined behaviour. Thus, I will retract this suggestion.