code: public static String escapeKeyword(String symbol) {
      if (swiftKeywords.contains(symbol)) {
        return "`" + symbol + "`";
      } else if (reservedSymbols.contains(symbol)) {
        return symbol + "$";
      } else {
        return symbol;
      }
    }
docs: Returns the escaped Pegasus symbol for use in Swift source code.
  
  Pegasus symbols must be of the form [A-Za-z_], so this routine simply checks if the
  symbol collides with a swift keyword, and if so, escapes it.
  
  (Because only fields are generated, symbols like hashCode do not collide with method names
  from Object and may be used).
  
  @param symbol the symbol to escape
  @return the escaped Pegasus symbol.