code: static boolean isMatchSymbol(final Symbol symbol) {
          if (!(symbol instanceof BasisSymbol)) {
              return false;
          }
          BasisSymbol basisSymbol = (BasisSymbol) symbol;
          Set<Symbol> uniqueSymbols = new HashSet<Symbol>();
          for (Object o : basisSymbol.getSymbols()) {
              Symbol s = (Symbol) o;
              if (isGapSymbol(s)) {
                  return false;
              }
              uniqueSymbols.add((Symbol) o);
          }
          return (uniqueSymbols.size() == 1);
      }
docs: Return true if the specified symbol represents an alignment match.
  
  @param symbol symbol
  @return true if the specified symbol represents an alignment match