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import { isArray } from './_internals/isArray.js'
export function flatten(list, input){  const willReturn = input === undefined ? [] : input
  for (let i = 0; i < list.length; i++){    if (isArray(list[ i ])){      flatten(list[ i ], willReturn)    } else {      willReturn.push(list[ i ])    }  }
  return willReturn}