From ec1a4b5d2b8a092bc2bbec86b6f0f04882c685a5 Mon Sep 17 00:00:00 2001
From: Patrick Shriwise <pshriwise@gmail.com>
Date: Tue, 5 Mar 2019 13:22:50 -0600
Subject: [PATCH] Adding documentation to create_xml_subelement methods.
 Removing old, now unused, path variables from those methods as well.

---
 openmc/cell.py     | 17 ++++++++++++++++-
 openmc/lattice.py  | 25 +++++++++++++++++--------
 openmc/universe.py | 18 +++++++++++++++++-
 3 files changed, 50 insertions(+), 10 deletions(-)

diff --git a/openmc/cell.py b/openmc/cell.py
index bb59b1d3a..fb39dd7ec 100644
--- a/openmc/cell.py
+++ b/openmc/cell.py
@@ -463,7 +463,23 @@ class Cell(IDManagerMixin):
         return memo[self]
 
     def create_xml_subelement(self, xml_element, memo=None):
+        """Add the cell's xml representation to an incoming xml element
 
+        Parameters
+        ----------
+        xml_element : xml.etree.ElementTree.Element
+            XML element to be added to
+
+        memo : dict or None
+            A dictionary containing sets of universe, lattice, cell, and surface
+            id sets already written to the xml_element. This parameter
+            is used internally and should not be specified by the user.
+
+        Returns
+        -------
+        None
+
+        """
         element = ET.Element("cell")
         element.set("id", str(self.id))
 
@@ -500,7 +516,6 @@ class Cell(IDManagerMixin):
             # thus far.
             def create_surface_elements(node, element, memo=None):
                 if isinstance(node, Halfspace):
-                    path = "./surface[@id='{}']".format(node.surface.id)
                     if memo and node.surface.id in memo['surfaces']:
                         return
                     if memo is not None:
diff --git a/openmc/lattice.py b/openmc/lattice.py
index dff00306a..0434d626b 100644
--- a/openmc/lattice.py
+++ b/openmc/lattice.py
@@ -753,11 +753,24 @@ class RectLattice(Lattice):
                     0 <= idx[2] < self.shape[2])
 
     def create_xml_subelement(self, xml_element, memo=None):
-        # Determine if XML element already contains subelement for this Lattice
-        path = './lattice[@id=\'{0}\']'.format(self._id)
-        test = xml_element.find(path)
+        """Add the lattice xml representation to an incoming xml element
 
-        # If the element does contain the Lattice subelement, then return
+        Parameters
+        ----------
+        xml_element : xml.etree.ElementTree.Element
+            XML element to be added to
+
+        memo : dict or None
+            A dictionary containing sets of universe, lattice, cell, and surface
+            id sets already written to the xml_element. This parameter
+            is used internally and should not be specified by the user.
+
+        Returns
+        -------
+        None
+
+        """
+        # If the element already contains the Lattice subelement, then return
         if memo and self._id in memo['lattices']:
             return
         if memo is not None:
@@ -1275,10 +1288,6 @@ class HexLattice(Lattice):
             return g < self.num_rings and 0 <= idx[2] < self.num_axial
 
     def create_xml_subelement(self, xml_element, memo=None):
-        # Determine if XML element already contains subelement for this Lattice
-        path = './hex_lattice[@id=\'{0}\']'.format(self._id)
-        test = xml_element.find(path)
-
         # If the element does contain the Lattice subelement, then return
         if memo and self._id in memo['lattices']:
             return
diff --git a/openmc/universe.py b/openmc/universe.py
index ea8c7f294..e1c1e1b0c 100644
--- a/openmc/universe.py
+++ b/openmc/universe.py
@@ -512,9 +512,25 @@ class Universe(IDManagerMixin):
         return memo[self]
 
     def create_xml_subelement(self, xml_element, memo=None):
+        """Add the universe xml representation to an incoming xml element
+
+        Parameters
+        ----------
+        xml_element : xml.etree.ElementTree.Element
+            XML element to be added to
+
+        memo : dict or None
+            A dictionary containing sets of universe, lattice, cell, and surface
+            id sets already written to the xml_element. This parameter
+            is used internally and should not be specified by the user.
+
+        Returns
+        -------
+        None
+
+        """
         # Iterate over all Cells
         for cell_id, cell in self._cells.items():
-            path = "./cell[@id='{}']".format(cell_id)
 
             # If the cell was not already written, write it
             if memo and cell_id in memo['cells']: