make render_heading reusable

nbconvert.py

@@ -109,13 +109,13 b' class Converter(object):'
 class ConverterRST(Converter):
     extension = 'rst'
     figures_counter = 0
+    heading_level = {1: '=', 2: '-', 3: '`', 4: '\'', 5: '.', 6: '~'}
 
     def render_heading(self, cell):
         """convert a heading cell to rst
 
         Returns list."""
-        heading_level = {1: '=', 2: '-', 3: '`', 4: '\'', 5: '.', 6: '~'}
-        marker = heading_level[cell.level]
+        marker = self.heading_level[cell.level]
         return ['{0}\n{1}\n'.format(cell.source, marker * len(cell.source))]
 
     def render_code(self, cell):

tests/test_simple.py

@@ -55,9 +55,8 b' def test_render_heading():'
         nt.assert_true(isinstance(rst_list, list))  # render should return a list
         rst_str = "".join(rst_list)
         # Confirm rst content
-        heading_level = {1: '=', 2: '-', 3: '`', 4: '\'', 5: '.', 6: '~'}
         chk_str = "Test for heading type H{0}\n{1}\n".format(
-             level, heading_level[level] * 24)
+             level, c.heading_level[level] * 24)
         nt.assert_equal(rst_str, chk_str)