test: fixing wrong curie prefix expectation

CURIE prefixes can start with an underscore ('_'). This patch adds a
test case to validate it.

Signed-off-by: Silvano Cirujano Cuesta <silvano.cirujano-cuesta@siemens.com>

Author: Silvanoc

tests/test_utils/test_metamodelcore.py

@@ -73,6 +73,7 @@ def test_curie(self):
         self.assertTrue(Curie.is_valid("type"))
         self.assertEqual(":type", Curie(":type"))
         self.assertTrue(Curie.is_valid(":type"))
+        self.assertTrue(Curie.is_valid("_abc:123"))
         self.assertTrue(Curie.is_valid("WIKIDATA_PROPERTY:P854"))
         self.assertTrue(Curie.is_valid("WIKIDATA.PROPERTY:P854"))
         self.assertTrue(Curie.is_valid("CL:0000001"))