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import {concat} from './concat'import {filter} from './filter'import {includes} from './includes'
export function symmetricDifference(x, y) {  if (arguments.length === 1) {    return _y => symmetricDifference(x, _y)  }
  return concat(    filter(value => !includes(value, y), x),    filter(value => !includes(value, x), y)  )}