Nested enums now translate to nested states

[thedrow]

Fixes #404.

This needs documentation but I don't know which version this feature will released on.
I'm assuming 0.9.0. Am I correct?

[coveralls]

Coverage decreased (-0.04%) to 98.481% when pulling 2d9e508 on thedrow:nested-enums-to-nested-state into 070b450 on pytransitions:master.

[aleneum]

That looks good to me. Some minor tweeks need to be done though (for instance here). Did you check whether the resulting Graphviz graphs look okay? Is it possible to determine the actual state and can you use auto transitions?:

from enum import Enum, auto
class Foo(Enum):
  A = auto()  # 1 
  B = auto()  # 2

class Bar(Enum):
  FOO = Foo
  C = auto()  # 1

m = HierarchicalMachine(states=Bar, initial=Bar.C)
m.to_FOO_A()  # does this work?
assert m.is_C() is False  # a check by state.value would return True though 

[thedrow]

Do we need to remove this check?

transitions/transitions/extensions/nesting.py

Lines 27 to 28 in 070b450

	if isinstance(model_states, Enum):
	res[model_states.name] = {} # since enum cannot be nested we do not need an OrderedDict here

[thedrow]

Setting the initial to Bar.C uncovered a bug in this PR that causes the test to fail because of the Graphvis extension.
I fixed it now. I'll generate a graph and see if it looks correct.

[thedrow]

Looks right to me :)

[aleneum]

Merged! Thanks again for your valuable contributions!

Setting the initial to Bar.C uncovered a bug in this PR that causes the test to fail because of the Graphvis extension.

this is comparable to #400 and should be fixed with 0a66a36. An additional test in set_node_style should not be necessary anymore. I removed it.

Sidenote: Enums with identical values cannot be distinguished. That should be at least mentioned in the documentation.

[thedrow]

Do we need to remove this check?

transitions/transitions/extensions/nesting.py

Lines 27 to 28 in 070b450

	if isinstance(model_states, Enum):
	res[model_states.name] = {} # since enum cannot be nested we do not need an OrderedDict here

Wait, what about this? Nevermind, I see your commits.
But check my comments.