code: public String getProperty(String expression) {
      if (expression == null || expression.length() == 0) { return expression; }
      for (int i = 0; i < expression.length(); i++) {
        char c = expression.charAt(i);
        if (c == Nested) {
          return expression.substring(0, i);
        } else if (c == MappedStart || c == IndexedStart) { return expression.substring(0, i); }
      }
      return expression;
    }
docs: Return the property name from the property expression.
  
  @param expression The property expression
  @return The property name