Collection {#143 ▼
  #items: array:2 [▼
    "poniedziałek" => Collection {#517 ▼
      #items: array:2 [▼
        0 => Event {#510 ▶}
        1 => Event {#511 ▶}
      ]
    }
    "wtorek" => Collection {#527 ▼
      #items: array:1 [▼
        0 => Event {#512 ▶}
      ]
    }
  ]
}