class_docstr: A tree structure which has a node :class:`.Metric` and some children. Upon execution, the node is called with the
  input and its output is passed to each of the children. A dict is updated with the results.
  
  .. note::
  
     If the node output is already a dict (i.e. the node is a standalone metric), this is unwrapped before passing the
     **first** value to the children.
  
  Args:
      metric (Metric): The metric to act as the root node of the tree / subtree
class_docstr_tok: ["A","tree","structure","which","has","a","node",":","class",":","`",".Metric","`","and","some","children",".","Upon","execution",",","the","node","is","called","with","the","input","and","its","output","is","passed","to","each","of","the","children",".","A","dict","is","updated","with","the","results",".","..","note",":",":","If","the","node","output","is","already","a","dict","(","i.e",".","the","node","is","a","standalone","metric",")",",","this","is","unwrapped","before","passing","the","*","*","first","*","*","value","to","the","children",".","Args",":","metric","(","Metric",")",":","The","metric","to","act","as","the","root","node","of","the","tree","\/","subtree"]
docstr: Add a child to this node of the tree
  
  Args:
      child (Metric): The child to add
docstr_tok: ["Add","a","child","to","this","node","of","the","tree","Args",":","child","(","Metric",")",":","The","child","to","add"]
code: def add_child(self, child):
      """Add a child to this node of the tree
  
      Args:
          child (Metric): The child to add
      """
      self.children.append(child)
  
imports: import inspect
  from torchbearer import Metric, no_grad
label_desc: Use image node_id 3 for calling the MetricTree obj's underlying member method code with example usage: obj.add_child(child) without return types