How to stop calling data() function for the child items in a tree view initially

[DURGAPRASAD NEELAM]

I have re-implemented below functions in my model.

QVariant data( const QModelIndex & index, int role = Qt::DisplayRole ) const ;
    bool setData(const QModelIndex & index, const QVariant & value, int role = Qt::EditRole);
    Qt::ItemFlags flags( const QModelIndex &index ) const;
    QVariant headerData( int section, Qt::Orientation orientatio, int role = Qt::DisplayRole ) const;
    virtual QModelIndex index( int row, int column, const QModelIndex &parent = QModelIndex() ) const;
    virtual QModelIndex parent( const QModelIndex &index ) const;
    int rowCount( const QModelIndex &parent = QModelIndex() ) const;
    virtual bool hasChildren ( const QModelIndex & parent = QModelIndex() ) const;
    int columnCount( const QModelIndex &parent = QModelIndex() ) const { return m_columnCount; }

QVariant data( const QModelIndex & index, int role = Qt::DisplayRole ) const ;
    bool setData(const QModelIndex & index, const QVariant & value, int role = Qt::EditRole);
    Qt::ItemFlags flags( const QModelIndex &index ) const;
    QVariant headerData( int section, Qt::Orientation orientatio, int role = Qt::DisplayRole ) const;
    virtual QModelIndex index( int row, int column, const QModelIndex &parent = QModelIndex() ) const;
    virtual QModelIndex parent( const QModelIndex &index ) const;
    int rowCount( const QModelIndex &parent = QModelIndex() ) const;
    virtual bool hasChildren ( const QModelIndex & parent = QModelIndex() ) const;
    int columnCount( const QModelIndex &parent = QModelIndex() ) const { return m_columnCount; }

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And I am using proxy model too for filtering data, here i re-implement filterAcceptsRow().
If more info is needed, Please let me know.

Thnaks.