Attempt to refactor a bit of context, new count transform that counts the calls, new bonobo.structs package with basic data structures, removal of blessings.

tests/structs/test_graphs.py

@@ -0,0 +1,42 @@
+import pytest
+
+from bonobo import Graph, BEGIN
+
+identity = lambda x: x
+
+
+def test_graph_outputs_of():
+    g = Graph()
+
+    # default graph only node
+    assert len(g.outputs_of(BEGIN)) == 0
+
+    # unexisting node
+    with pytest.raises(KeyError):
+        g.outputs_of(0)
+
+    # create node
+    assert len(g.outputs_of(0, create=True)) == 0
+    assert len(g.outputs_of(0)) == 0
+
+
+def test_graph_add_component():
+    g = Graph()
+
+    assert len(g.nodes) == 0
+
+    g.add_node(identity)
+    assert len(g.nodes) == 1
+
+    g.add_node(identity)
+    assert len(g.nodes) == 2
+
+
+def test_graph_add_chain():
+    g = Graph()
+
+    assert len(g.nodes) == 0
+
+    g.add_chain(identity, identity, identity)
+    assert len(g.nodes) == 3
+    assert len(g.outputs_of(BEGIN)) == 1