title: How to hide ttk Treeitem indicators in a Python GUI
body: <p>I'm building a Python GUI application using ttk treeviews. On Linux, when a Treeitem has child items, it displays an arrow to show that the row can be expanded. I want to hide this indicator arrow (I am using other ways to hint that the row can be expanded). How can I do this?</p>
  
  <p>If I run <code>Style().element_names()</code> I see that there's a Treeview element and a Treeitem.indicator element. If I run <code>Style().configure("Treeview", padding=50)</code>, I see the padding style get applied when I create the treeview, so I feel confident that any style I correctly apply to Treeitem.indicator should be visible also. </p>
  
  <p>Running <code>Style().element_options("Treeitem.indicator")</code>, I see <code>('-foreground', '-indicatorsize', '-indicatormargins')</code>.  Running <code>Style().lookup("Treeitem.indicator", "foreground")</code> gives me <code>"#000000"</code>, so it appears that value is initialized. If I try <code>Style().configure("Treeview", foreground="#123456")</code> I don't see the indicator arrow change color, though running <code>Style.lookup("Treeitem.indicator", "foreground")</code> shows me <code>"#123456"</code> as expected. My plan was to set the indicatorsize to 0 to make the arrow go away entirely, but I cannot even successfully edit the color. What am I doing wrong here and is there a better way to hide the indicator? In case it matters, I'm running Python 3.5.0.</p>