docs: def get_child_by_name(self, childname):
          """Get a child node of the current instance by its name.
  
          :param childname: the name of the required child node.
          :type childname: str
          :returns: the first child node found with name `childname`.
          :rtype: Node or None
          """
          _childs = [_child for _child in self.childs if _child.name==childname]
          if len(_childs)>1:
              logger.warning("%s.get_child_by_name: node:«%s» has more than 1 childnode with name=«%s»." % (self.__class__.__name__, self.name, childname))
          if len(_childs)==0:
              _childnode = None
          else:
              _childnode = _childs[0] 
          return _childnode