code: function registerDual(numberType, numericType, checkFn, toJSONSchema) {
  		context.registerType(numberType, 'number', checkFn, numberType, extra => toJSONSchema('number', extra))
  
  		context.registerType(numericType, 'string', value => {
  			let numberValue = toNumber(value)
  			checkFn(numberValue)
  			return numberValue
  		}, numericType, () => ({
  				type: 'string',
  				format: numericType
  			}))
  	}
docs: Register number and numeric dual basic types
  @param {string} numberType
  @param {string} numericType
  @param {Function} checkFn
  @param {function(string, *):Object} toJSONSchema
  @private