class_docstr: Base class of modifiers.
  
  The `modify` method is called for a function with inputs in a graph topological order
  when you call the GraphConverter(<modifiers>).convert(<root variable>) method.
class_docstr_tok: ["Base","class","of","modifiers",".","The","`","modify","`","method","is","called","for","a","function","with","inputs","in","a","graph","topological","order","when","you","call","the","GraphConverter","(","<","modifiers",">",")",".convert","(","<","root","variable",">",")","method","."]
code: def _force_list(self, o):
      if isinstance(o, (tuple)):
          return list(o)
      if not isinstance(o, (list)):
          return [o]
  
imports: from collections import defaultdict
  import nnabla
  import nnabla.functions
label_desc: Use image node_id 4 for calling the FunctionModifier obj's underlying member method code with example usage: obj._force_list(o) and returns: list, list