Add a C{Node} to the C{KBucket}.  Return True if successful,
        False if the bucket is full.

        If the bucket is full, keep track of node in a replacement list,
        per section 4.1 of the paper.

def add_node(self, node):
        """
        Add a C{Node} to the C{KBucket}.  Return True if successful,
        False if the bucket is full.

        If the bucket is full, keep track of node in a replacement list,
        per section 4.1 of the paper.
        """
        if node.id in self.nodes:
            del self.nodes[node.id]
            self.nodes[node.id] = node
        elif len(self) < self.ksize:
            self.nodes[node.id] = node
        else:
            if node.id in self.replacement_nodes:
                del self.replacement_nodes[node.id]
            self.replacement_nodes[node.id] = node
            return False
        return True