code: def _override_cfg(container, yamlkeys, value):
      
  
      key = yamlkeys[0]
      rest = yamlkeys[1:]
  
      if len(rest) == 0:
          # no rest means we found the key to update.
          container[key] = value
  
      elif key in container:
          # still need to find the leaf in the tree, so recurse.
          _override_cfg(container[key], rest, value)
  
      else:
          # need to create a sub-tree down to the leaf to insert into.
          subtree = {}
          _override_cfg(subtree, rest, value)
          container[key] = subtree
docs: Override a hierarchical key in the config, setting it to the value.
  
      Note that yamlkeys should be a non-empty list of strings.