code: def safe_round(number, ndigits):
      ret = None
      if number is not None:
          ret = round(number, ndigits)
      return ret
  
imports: import csv
  import os
  import shutil
  import subprocess
  import tempfile
  import unittest
  import matplotlib
  from six.moves import xrange
  from pyalgotrade import dataseries
label_desc: Use image node_id 12 for calling a global function with example usage: safe_round(number, ndigits) and returns: ret