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

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