Fix circular ref between mesh and nodes and elements (#350)

* Fix circular ref between mesh and nodes and elements

* try fix

ansys/dpf/core/collection.py

@@ -41,11 +41,6 @@ class Collection:
         default is ``None``, in which case an attempt is made to use the global
         server.
 
-    Examples
-    --------
-    >>> from ansys.dpf import core as dpf
-    >>> coll = dpf.Collection(dpf.types.field)
-
     """
 
     def __init__(self, collection=None,

ansys/dpf/core/meshed_region.py

@@ -133,9 +133,7 @@ def elements(self):
         DPF Elements object with 8 elements
 
         """
-        if self._elements is None:
-            self._elements = Elements(self)
-        return self._elements
+        return Elements(self)
 
     @property
     def nodes(self):
@@ -158,9 +156,7 @@ def nodes(self):
         81
 
         """
-        if self._nodes is None:
-            self._nodes = Nodes(self)
-        return self._nodes
+        return Nodes(self)
 
     @property
     def unit(self):

tests/test_workflow.py

@@ -655,6 +655,7 @@ def test_create_on_other_server2_workflow(local_server):
 @pytest.mark.xfail(raises=dpf.core.errors.ServerTypeError)
 @conftest.raises_for_servers_version_under('3.0')
 def test_create_on_other_server_with_ip_workflow(local_server):
+    dpf.core.start_local_server()
     disp_op = op.result.displacement()
     max_fc_op = op.min_max.min_max_fc(disp_op)
     workflow = dpf.core.Workflow()