code: def safe_round(value, digits):
      if value is not None:
          value = round(value, digits)
      return value
  
file_path: pyalgotrade/samples/tutorial-3.py
imports: from pyalgotrade import strategy
  from pyalgotrade.barfeed import quandlfeed
  from pyalgotrade.technical import ma
  from pyalgotrade.technical import rsi
label_desc: Use image node_id 1 for calling a global function with example usage: safe_round(value, digits) and returns: value