docs: function collate (columns, filter) {
    return function (words, cb) {
      const entry = columns.reduce((entry, column, index) => {
        if (column === null) {
          return entry
        }
  
        if (!words[index]) {
          return entry
        }
  
        if (words[index].toLowerCase() === column.toLowerCase()) {
          return entry
        }
  
        const amend = {}
        amend[column] = words[index]
        return Object.assign({}, entry, amend)
      }, {})
  
      const filtered = filter(entry)
  
      if (filtered) {
        this.push(filtered)
      }
      cb()
    }
  }