Add test for PC-query with paths and fix bug

Author: bgyori

pybiopax/paths.py

@@ -87,7 +87,7 @@ def find_objects(start_obj: BioPaxObject, path_str: str) -> List[BioPaxObject]:
 def _get_object_list(val):
     if isinstance(val, BioPaxObject):
         return [val]
-    elif isinstance(val, list):
+    elif isinstance(val, (list, set)):
         return [v for v in val if isinstance(v, BioPaxObject)]
     else:
         return []

pybiopax/tests/test_paths.py

@@ -1,5 +1,6 @@
 import pytest
 from pybiopax.biopax import *
+from pybiopax import model_from_pc_query
 from pybiopax.paths import find_objects, BiopaxClassConstraintError
 
 
@@ -74,3 +75,12 @@ def test_recursive():
     objects = find_objects(c2, 'member_physical_entity*')
     assert len(objects) == 2, objects
     assert set(objects) == {p1, c1}
+
+
+def test_multi_step():
+    model = model_from_pc_query('pathsfromto', ['MAP2K1'], ['MAPK1'])
+    bcr = model.objects['BiochemicalReaction_4f689747397d98089c551022a3ae2d88']
+    assert len(find_objects(bcr, 'left')) == 1
+    assert len(find_objects(bcr, 'left/entity_reference')) == 1
+    objs = find_objects(bcr, 'left/entity_reference/entity_reference_of')
+    assert len(objs) == 10