format trees

app.py

@@ -1,6 +1,10 @@
 import matplotlib
 matplotlib.use('Agg')
 
+import os
+os.system('Xvfb :1 -screen 0 1600x1200x16  &')    # create virtual display with size 1600x1200 and 16 bit color. Color can be changed to 24 or 8
+os.environ['DISPLAY']=':1.0'   
+
 import gradio
 import benepar
 import spacy

packages.txt

@@ -1,2 +1,3 @@
+xvfb
 ghostscript
 python3-tk