How to use the graphistry.pygraphistry.util.warn function in graphistry

def _check_dataset_size(self, elist, nlist):
        edge_count = len(elist.index)
        node_count = len(nlist.index)
        graph_size = edge_count + node_count
        if edge_count > 8e6:
            util.error('Maximum number of edges (8M) exceeded: %d.' % edge_count)
        if node_count > 8e6:
            util.error('Maximum number of nodes (8M) exceeded: %d.' % node_count)
        if graph_size > 1e6:
            util.warn('Large graph: |nodes| + |edges| = %d. Layout/rendering might be slow.' % graph_size)

def bind(df, pbname, attrib, default=None):
            bound = getattr(self, attrib)
            if bound:
                if bound in df.columns.tolist():
                    df[pbname] = df[bound]
                else:
                    util.warn('Attribute "%s" bound to %s does not exist.' % (bound, attrib))
            elif default:
                df[pbname] = df[default]