code: def circular(adjacency_mat, directed=False):
      
  
      if issparse(adjacency_mat):
          adjacency_mat = adjacency_mat.tocoo()
  
      num_nodes = adjacency_mat.shape[0]
  
      t = np.linspace(0, 2 * np.pi, num_nodes, endpoint=False, dtype=np.float32)
  
      # Visual coordinate system is between 0 and 1, so generate a circle with
      # radius 0.5 and center it at the point (0.5, 0.5).
      node_coords = (0.5 * np.array([np.cos(t), np.sin(t)]) + 0.5).T
  
      line_vertices, arrows = _straight_line_vertices(adjacency_mat,
                                                      node_coords, directed)
  
      yield node_coords, line_vertices, arrows
docs: Places all nodes on a single circle.
  
      Parameters
      ----------
      adjacency_mat : matrix or sparse
          The graph adjacency matrix
      directed : bool
          Whether the graph is directed. If this is True, is will also
          generate the vertices for arrows, which can be passed to an
          ArrowVisual.
  
      Yields
      ------
      (node_vertices, line_vertices, arrow_vertices) : tuple
          Yields the node and line vertices in a tuple. This layout only yields a
          single time, and has no builtin animation