old_contents: export default function humanizeOperator(operator) {
  	if (operator === '$gte') {
  		return ''
  	}
  	else if (operator === '$lte') {
  		return 'at most'
  	}
  	else if (operator === '$eq') {
  		return 'exactly'
  	}
  }
  
new_contents: export default function humanizeOperator(operator) {
  	if (operator === '$gte') {
  		return ''
  	}
  	else if (operator === '$lte') {
  		return 'at most'
  	}
  	else if (operator === '$eq') {
  		return 'exactly'
  	}
  	throw new TypeError(`humanizeOperator does not recognize "${operator}" as being an operator.`)
  }
  
subject: add a catch-all error to humanizeOperator