docstr: Return children traversable from `wrt_inputs` in the forward graph topological order.
docstr_tok: ["Return","children","traversable","from","`","wrt_inputs","`","in","the","forward","graph","topological","order","."]
code: def _get_children(self, wrt_inputs):
      """
      Return children traversable from `wrt_inputs` in the forward graph topological order.
      """
      children = set()
  
      def dfs(node):
          if node in children:
              return
  
          for f in node.function_references:
              if f.info.type_name == "GradEndFunction":
                  continue
              for o in f.outputs:
                  if o in children:
                      continue
                  dfs(o)
                  children.add(o)
  
      for inp in wrt_inputs:
          if inp is None:
              continue
          dfs(inp)
  
      return children
  
imports: import numpy
  from collections import OrderedDict
  import nnabla
  import nnabla.functions
  from nnabla.function import PythonFunction
  from .backward_functions import registry
label_desc: Use image node_id 5 for calling the Grad obj's underlying member method code with example usage: obj._get_children(wrt_inputs) and returns: children