Laravel illluminati集合删除重复项目

I have a collection called $applied_exams which contain following data

Collection {#2033 ▼#items: array:4 [▼
0 => {#2035 ▼
  +"post_id": 1
  +"designation_id": 9
  +"token_number": 438
  +"name": "TECHNICIAN TELECOM"
  +"adb": "2074-06-23"
  +"ContainMultiplePost": false
  +"Group_id": 8
}
1 => {#2034 ▼
  +"post_id": 11
  +"designation_id": 1
  +"token_number": 740
  +"name": "DEPUTY MANAGER TELECOM"
  +"adb": "2074-06-25"
  +"ContainMultiplePost": false
  +"Group_id": 1
}
2 => {#2040 ▼
  +"post_id": 3
  +"designation_id": 12
  +"token_number": 2810
  +"name": "ASST. BUSINESS OFFICER"
  +"adb": "2074-10-24"
  +"ContainMultiplePost": true
  +"Group_id": 7
}
3 => {#2039 ▼
  +"post_id": 2
  +"designation_id": 8
  +"token_number": 2811
  +"name": "ASST. ADMINISTRATIVE OFFICER"
  +"adb": "2074-10-24"
  +"ContainMultiplePost": true
  +"Group_id": 7
}]}

I want to unset the data with duplicate group_id. I only want one data of one group_id. In this case I just want the $applied_exam[3] to be removed because group_id is same as $applied_exams[2]. Please help. Thanks

when retriving items use unique function

$unique_applied_exams = $applied_exams->unique('group_id');