old_contents: 'use strict';
  
  const { addAllErrorHandlers } = require('./error');
  
  const addOperator = {
    check (opVal) {
      if (opVal !== 2) { return; }
  
      return 'value cannot be equal to 2';
    },
  
    attribute: ['string'],
  
    argument: ['string', 'integer[]', 'boolean[]', 'null[]'],
  };
  
  // All patch operators
  const operators = {
    _add: addOperator,
  };
  
  const OPERATORS = addAllErrorHandlers({ operators });
  
  module.exports = {
    OPERATORS,
  };
  
new_contents: 'use strict';
  
  const { addAllErrorHandlers } = require('./error');
  
  const addOperator = {
    check (opVal) {
      if (opVal !== 2) { return; }
  
      return 'value cannot be equal to 2';
    },
  
    attribute: ['integer', 'number'],
  
    argument: ['integer', 'number', 'null'],
  
    apply (attrVal, opVal) {
      const opValA = opVal == null ? 0 : opVal;
      return attrVal + opValA;
    },
  };
  
  // All patch operators
  const operators = {
    _add: addOperator,
  };
  
  const OPERATORS = addAllErrorHandlers({ operators });
  
  module.exports = {
    OPERATORS,
  };
  
subject: Improve _add operator