Cannot assign to non-existent property - QtObject

[TheIndependentAquarius]

import QtQuick 2.0
 
Item
{  
  id     : mainWindow
  width  : 1024
  height : 768
 
  QtObject
  {
      id: anisha
      property url theme;
  }
 
  anisha.theme: "ddsad";
}

import QtQuick 2.0

Item
{  
  id     : mainWindow
  width  : 1024
  height : 768

  QtObject
  {
      id: anisha
      property url theme;
  }

  anisha.theme: "ddsad";
}

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Error:

Cannot assign to non-existent property "anisha"
    anisha.theme: "ddsad";

Cannot assign to non-existent property "anisha"
    anisha.theme: "ddsad";

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What is the way to use QtObject?