class_docstr: For producing HTML side by side comparison with change highlights.
  
  This class can be used to create an HTML table (or a complete HTML file
  containing the table) showing a side by side, line by line comparison
  of text with inter-line and intra-line change highlights.  The table can
  be generated in either full or contextual difference mode.
  
  The following methods are provided for HTML generation:
  
  make_table -- generates HTML for a single side by side table
  make_file -- generates complete HTML file with a single side by side table
  
  See tools/scripts/diff.py for an example usage of this class.
docstr: Create unique anchor prefixes
docstr_tok: ["Create","unique","anchor","prefixes"]
code: def _make_prefix(self):
      """Create unique anchor prefixes"""
  
      # 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]
  
imports: from heapq import nlargest
  from collections import namedtuple
  from types import GenericAlias
  import re
label_desc: Use image node_id 8 for calling the HtmlDiff obj's underlying member method code with example usage: obj._make_prefix() without return types