Merge columns in QTreeView

[Ginsengelf]

Hi, I have a QTreeView with a QStandardItemModel. Since the entries in the top level items can be a little long (and all columns except the first one are empty) I would like them to use the space of the other columns as well instead of just the first column:
This is what I've got:

Col1        | Col2        | Col3
>Top_Le...  |
  >0        |  1          |  2
  >3        |  4          |  5
  >6        |  7          |  8

Col1        | Col2        | Col3
>Top_Le...  |
  >0        |  1          |  2
  >3        |  4          |  5
  >6        |  7          |  8

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This is what I want:

Col1        | Col2        | Col3
>Top_Level_With long_Text
  >0        |  1          | 2
  >3        |  4          | 5
  >6        |  7          | 8
>2nd_Top_Level_With long_Text
  >0        |  1          | 2
  >3        |  4          | 5
  >6        |  7          | 8

Col1        | Col2        | Col3
>Top_Level_With long_Text
  >0        |  1          | 2
  >3        |  4          | 5
  >6        |  7          | 8
>2nd_Top_Level_With long_Text
  >0        |  1          | 2
  >3        |  4          | 5
  >6        |  7          | 8

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In QTableView there is a method to set span on the cells, but I haven't found anything similar in QTreeView. I could use QTableView, but I like the expanding/collapsing feature of the tree.

Ginsengelf