Python: Additional tests for model-editor

We currently have some problems with these files, that we should fix
later down the line. See PR comment for more details.

python/ql/test/modelling/not-valid-package/not_in_pacakge_lib_copy.py

@@ -0,0 +1,2 @@
+def not_in_pacakge_lib_func(x, y):
+    return x + y

python/ql/test/modelling/not-valid-package/not_in_package_script_copy.py

@@ -0,0 +1,10 @@
+#!/usr/bin/env python
+
+import not_in_pacakge_lib_copy
+
+def not_in_package_script_func(x, y):
+    return x + y
+
+if __name__ == "__main__":
+    print(not_in_pacakge_lib_copy.not_in_pacakge_lib_func(1, 2))
+    print(not_in_package_script_func(3, 4))

python/ql/test/modelling/not-valid-package/possibly_lib_copy.py

@@ -0,0 +1,5 @@
+# model editor should allow modeling the functions defined in this file, even when the
+# file is not imported explicitly.
+
+def possibly_lib_func(x, y):
+    return x + y