code: def _gen_dimension_table(self):
          
          headers = ['Dimension Name', 'Description',
              'Global Size', 'Extents']
  
          table = []
          for dimval in sorted(self.dimensions(copy=False).itervalues(),
                               key=lambda dval: dval.name.upper()):
  
              table.append([dimval.name,
                  dimval.description,
                  dimval.global_size,
                  (dimval.lower_extent, dimval.upper_extent)])
  
          return table, headers
docs: 2D array describing each registered dimension
          together with headers - for use in __str__