fix: make write provenance return a graph and add niiri as default namespace

Author: satra

nipype/utils/provenance.py

@@ -17,8 +17,9 @@
 foaf = pm.Namespace("foaf", "http://xmlns.com/foaf/0.1/")
 dcterms = pm.Namespace("dcterms", "http://purl.org/dc/terms/")
 nipype_ns = pm.Namespace("nipype", "http://nipy.org/nipype/terms/")
+niiri = pm.Namespace("niiri", "http://nidm.nidash.org/iri/")
 
-get_id = lambda: nipype_ns[uuid1().hex]
+get_id = lambda: niiri[uuid1().hex]
 
 def safe_encode(x):
     """Encodes a python value for prov
@@ -66,7 +67,7 @@ def safe_encode(x):
 def write_provenance(results, filename='provenance', format='turtle'):
     ps = ProvStore()
     ps.add_results(results)
-    ps.write_provenance(filename=filename, format=format)
+    return ps.write_provenance(filename=filename, format=format)
 
 class ProvStore(object):
 
@@ -75,6 +76,7 @@ def __init__(self):
         self.g.add_namespace(foaf)
         self.g.add_namespace(dcterms)
         self.g.add_namespace(nipype_ns)
+        self.g.add_namespace(niiri)
 
     def add_results(self, results):
         if results.provenance: