text: # -*- coding: utf-8 -*-
  # Copyright (c) Vispy Development Team. All Rights Reserved.
  # Distributed under the (new) BSD License. See LICENSE.txt for more info.#!/usr/bin/env python3
  from ..util import _straight_line_vertices, issparse
  import numpy as np
  try:
      import networkx as nx
  except ModuleNotFoundError:
      import warnings
      warnings.warn(
          "Networkx not found, please install network to use its layouts")
      nx = None
  
  
  class NetworkxCoordinates:
      def __init__(self, graph=None, layout=None, **kwargs):
          """
          Converts :graph: into a layout. Can be used in conjunction with networkx layouts or using raw 2D-numpy arrays.
  
          Parameters
          ----------
          graph : a networkx graph.
          layout : str or dict or iterable-object of float32, optional
          - When :layout: is s string, a lookup will be performed in the networkx avaiable layouts.
          - When :layout: is a dict, it will be assumed that it takes the shape (key, value) = (node_id, 2D-coordinate).
          - When :layout: is numpy array it is assumed it takes the shape (number_of_nodes, 2).
          kwargs: dict, optional
          when layout is :str: :kwargs: will act as a setting dictionary for the layout function of networkx
          """
          if isinstance(graph, type(None)):
              raise ValueError("Requires networkx input")
          self.graph = graph
          self.positions = np.zeros((len(graph), 2), dtype=np.float32)
          # default random positions
          if isinstance(layout, type(None)):
              self.positions = np.random.rand(*self.positions.shape)
  
          # check for networkx
          elif isinstance(layout, str):
              if nx:
                  if not layout.endswith("_layout"):
                      layout += "_layout"  # append for nx
                  layout_function = getattr(nx, layout)
                  if layout_function:
                      self.positions = np.asarray(
                          [i for i in dict(layout_function(graph, **kwargs)).values()])
                  else:
                      raise ValueError("Check networkx for layouts")
              else:
                  raise ValueError("networkx not found")
          # assume dict from networkx; values are 2-array
          elif isinstance(layout, dict):
              self.positions = np.asarray([i for i in layout.values()])
  
          # assume given values
          elif isinstance(layout, np.ndarray):
              assert layout.ndim == 2
              assert layout.shape[0] == len(graph)
              self.positions = layout
          else:
              raise ValueError("Input not understood")
  
          # normalize coordinates
          self.positions = (self.positions - self.positions.min()) / \
              (self.positions.max() - self.positions.min())
          self.positions = self.positions.astype(np.float32)
  
      def __call__(self, adjacency_mat, directed=False):
          """
          Parameters
          ----------
          adjacency_mat : sparse adjacency matrix.
          directed : bool, default False
  
          Returns
          ---------
          (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
          """
          if issparse(adjacency_mat):
              adjacency_mat = adjacency_mat.tocoo()
          line_vertices, arrows = _straight_line_vertices(
              adjacency_mat, self.positions, directed)
  
          yield self.positions, line_vertices, arrows
  
      @property
      def adj(self):
          """Convenient storage and holder of the adjacency matrix for the :scene.visuals.Graph: function."""
          return nx.adjacency_matrix(self.graph)
  