function notContainsKey(key) {
                // if given key isn't present in the given field of the request, return a dict with error message
                if((req[field][key] === undefined)) {
                    const error = {}
                    error[key] = `Couldn't found the '${key}' in the request ${field}.`
                    return error
                }
                // otherwise, return false, as there's no error about that key
                return false
            }
// helper function used in mapping keys in given spec
helper function used in mapping keys in given spec
helper function used in mapping keys in given spec
function notContainsKey(key) {
                if((req[field][key] === undefined)) {
                    const error = {}
                    error[key] = `Couldn't found the '${key}' in the request ${field}.`
                    return error
                }
                return false
            }
function notContainsKey ( key ) { if ( ( req [ field ] [ key ] === undefined ) ) { const error = { } error [ key ] = ` ${ key } ${ field } ` return error } return false }
helper function used in mapping keys in given spec
helper function used in mapping keys in given spec
// if given key isn't present in the given field of the request, return a dict with error message // otherwise, return false, as there's no error about that key