docs: function _splitPath (keys) {
    var out
  
    if (util.isString(keys)) {
      out = []
      keys
        .split('.')
        .map(_segment('.'))
        .forEach(function (k) {
          k = (k || ' ').trim()
            .replace(/^([^[]+)\[(["']?)(.+)\2\]$/, function (m, m1, m2, m3) {
              if (m1 && m3) {
                out.push(m1, m3)
              }
              return ''
            })
          if (k) {
            out.push(k)
          }
        })
      keys = out
    }
    return keys
  }