update the C4AmaranthaceaePolyroot tree

example/trees4analyses_db/command.py

 
 from ete3 import Tree
+import sys
 
 f_l=["./C4AmaranthaceaePolyroot.nhx","./cyp_coding.Chrysithr_root.nhx"]
 
+
 def m_bl(t_n, m):
     t=Tree(t_n)
+    nb_root_children = len(t.get_children())
+    if nb_root_children > 2:
+        print("Unrooted tree")
+        sys.exit(1)
     for n in t.traverse():
         n.dist = n.dist * m
     out_n = t_n.replace(".nhx",".bl_%.2f.nhx" %(m))