The class Edge does not inherit from Node anymore,
instead the former class Node is renamed to Entity.
(This name was present before but deleted by now.)
To keep the graph structure, a new class Node also
inherits from Entity - without adding further
functionality. This way, everything works as before
but clean graph theoretic language is preserved.

Entity is the mother class of Node and Edge,
but instances of Node shoukd not be used.
Thus, it should be in the sence of comprehensability
to name Bus, Component, and Edge directly.

Asserts are meant for debugging. If a check should be there for end users
an if/raise statement is the way to go.

The import aliases where rarely used and thus more confusing than helpful.

The import aliases where rarely used and thus more confusing than helpful.

It makes sense to be precise if objects are Nodes, Edges, or Entities.
As the documentation mixes them (Edges were Nodes before), I tried to
figure or by reverse engeneering using solph.

According to
https://www.sphinx-doc.org/en/master/usage/extensions/extlinks.html,
there needs to be exactly one '%s' in every string in the config.

Fix/docs

As Entity.registry is deprecated anyway, this decorator should also go.

Automatic registration of `Node`s was deprecated,
so I removed it. There still was a ToDo note how
to improve it. I also deleted that one.

Adhere to graph language

The contents of tox.ini were replaced by those from solph.
There, legacy stuff like Travis CI were already removed.
Also, the tested python versions are more recent.
It worked locally, so in the sense of consistency,
I like the idea to have both files identical.

According to the dox, eq_ just saves characters.
We should not have that as a priority. (Nose is depracated anyway.)

The error messages were probably not checked before,
as the wording did not match. I fixed that.
(Content-wise they are similar to the formulations before.)

The flag was deprecated according to
https://docs.pytest.org/en/stable/how-to/capture-warnings.html

Fix unit tests

The file was pretty lonk and complex. Splitting it should make it
more comprehensible.

I assume this has been part of Entity as Entity was called Node before
and there was not proper Node class (edges should not be nodes).

Split network.network into submodules

Refine tests

This cleanup seems to have been forgotten when the Entity was
introduced to replace the former Node that was parent to Edge.

All subclasses to Node (Bus, Component, Sink, Source, and Transformer) do
not implement any additional functionality. This prepares their deletion.

Add tests for API to add Flows between existing Nodes

Deprecate child classes of Node

It makes no sense to deprecate subclasses to Node
without exposing Node as part of the API.

It might make sense to have the abstract superclass of
Node and Edge exposed in the API.