new_contents: """Graph coloring algorithms."""
  
  import networkx as nx
  
  
  def welsh_powell(graph):
      """Runs the Welsh-Powell algorithm to color a graph.
  
      Arguments:
          graph (networkx.Graph): a graph.
      """
      raise NotImplementedError('')
  
  
  def sequencial_coloring(graph):
      """Runs the Sequencial Coloring algorithm to color a graph.
  
      Arguments:
          graph (networkx.Graph): a graph.
      """
      raise NotImplementedError('')
  
  
  def class_coloring(graph):
      """Runs the Class Coloring algorithm to color a graph.
  
      Arguments:
          graph (networkx.Graph): a graph.
      """
      raise NotImplementedError('')
  
  
  def dsatur(graph):
      """Runs the Degree of Saturation heuristic algorithm to color a graph.
  
      Arguments:
          graph (networkx.Graph): a graph.
      """
      raise NotImplementedError('')
  
subject: Add coloring module