Azure Analysis Service - TMSL Merge Partition script

I am trying to merge existing table partition in Azure Analysis Service to main table using below TMSL script.

{   
  'mergePartitions': {   
    'target': {   
      'database': 'AASDatabase',   
      'table': 'sales',   
      'partition': 'Partition'   
    },   
    'sources': [   
      {   
        'database': 'AASDatabase',   
        'table': 'sales',   
        'partition': 'sales_20220901'   
      }  
    ]   
  }   
}

Below is the error I am facing

I have only one partition 'sales_20220901' which I want to merge back to main table to make it as a whole table

Could someone help me to understand the issue?