code: def escape(identifier, ansi_quotes, should_quote):
      
      if not should_quote(identifier):
          return identifier
  
      quote = '"' if ansi_quotes else '`'
      identifier = identifier.replace(quote, 2*quote)
      return '{0}{1}{2}'.format(quote, identifier, quote)
docs: Escape identifiers.
  
      ANSI uses single quotes, but many databases use back quotes.