add two more tutorials

tutorial/02_inheritance.py

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+
+# The following meta-model has an inheritance relation:
+
+mm_cs = """
+    MyAbstractClass:Class {
+        abstract = True;
+    }
+
+    MyConcreteClass:Class
+
+    :Inheritance (MyConcreteClass -> MyAbstractClass)
+
+    Z:Class
+
+    myZ:Association (MyAbstractClass -> Z) {
+        target_lower_cardinality = 1;
+    }
+
+"""
+
+# Note that we didn't give our inheritance link a name. A unique name will be auto-generated by the parser.
+
+
+# A (non-conforming) instance:
+
+m_nonconform_cs = """
+    cc:MyConcreteClass
+    z:Z
+"""
+
+
+# Check conformance:
+
+from state.devstate import DevState
+from bootstrap.scd import bootstrap_scd
+# from concrete_syntax.textual_od import parser
+# from framework.conformance import Conformance, render_conformance_check_result
+from util import loader
+
+state = DevState()
+mmm = bootstrap_scd(state)
+
+mm = loader.parse_and_check(state, mm_cs, mmm, "mm")
+
+print("should be non-conform:")
+m_nonconform = loader.parse_and_check(state, m_nonconform_cs, mm, "m_nonconform")
+
+
+# The reason for the non-conformance is that all cardinalities and constraints are inherited. Therefore 'MyConcreteClass' must have at least one outgoing 'myZ' link as well.
+
+# We fix the non-conformance by adding this link:
+
+m_conform_cs = m_nonconform_cs + """
+    :myZ (cc -> z)
+"""
+
+# Now everything will be fine
+
+print("should be conform:")
+m_conform = loader.parse_and_check(state, m_conform_cs, mm, "m_conform")
+print("OK")
+
+
+# On to the next tutorial...