code: public static IndexOperator getIndexOperator(String operator)
      {
          if (operator.equals("="))
          {
              return IndexOperator.EQ;
          }
          else if (operator.equals(">="))
          {
              return IndexOperator.GTE;
          }
          else if (operator.equals(">"))
          {
              return IndexOperator.GT;
          }
          else if (operator.equals("<"))
          {
              return IndexOperator.LT;
          }
          else if (operator.equals("<="))
          {
              return IndexOperator.LTE;
          }
  
          return null;
      }
docs: Returns IndexOperator from string representation
  @param operator - string representing IndexOperator (=, >=, >, <, <=)
  @return IndexOperator - enum value of IndexOperator or null if not found