code: def _make_prefix(self):
          
  
          # Generate a unique anchor prefix so multiple tables
          # can exist on the same HTML page without conflicts.
          fromprefix = "from%d_" % HtmlDiff._default_prefix
          toprefix = "to%d_" % HtmlDiff._default_prefix
          HtmlDiff._default_prefix += 1
          # store prefixes so line format method has access
          self._prefix = [fromprefix,toprefix]
docs: Create unique anchor prefixes