old_contents: import os
  from pyGATB.graph import Graph
  
  F_NAME='celegans_reads.h5'
  
  print ("File size: %.d kb" % (os.stat(F_NAME).st_size / 1024))
  
  graph = Graph('-in %s' % F_NAME)
  
  for i, node in enumerate(graph):
      print('{}: {!r}'.format(i, node))
      if i > 10: break
  
new_contents: # we import pyGATB Graph
  from pyGATB.graph import Graph
  
  # We will use a file containing a De Bruijn Graph stored
  # in HDF5 format; file created using dbgh5 tool provided
  # with GATB-Core. (This file is located next to this snippet)
  F_NAME='celegans_reads.h5'
  
  # We create the graph
  graph = Graph('-in %s' % F_NAME)
  
  # We iterate over some nodes
  for i, node in enumerate(graph):
      print('{}: {!r}'.format(i, node))
      if i > 10: break
  
subject: update snippet