code: def interval_graph(intervals):
      """Generates an interval graph for a list of intervals given.
  
      In graph theory, an interval graph is an undirected graph formed from a set
      of closed intervals on the real line, with a vertex for each interval
      and an edge between vertices whose intervals intersect.
      It is the intersection graph of the intervals.
  
      More information can be found at:
      https://en.wikipedia.org/wiki/Interval_graph
  
      Parameters
      ----------
      intervals : a sequence of intervals, say (l, r) where l is the left end,
      and r is the right end of the closed interval.
  
      Returns
      -------
      G : networkx graph
  
      Examples
      --------
      >>> intervals = [(-2, 3), [1, 4], (2, 3), (4, 6)]
      >>> G = nx.interval_graph(intervals)
      >>> sorted(G.edges)
      [((-2, 3), (1, 4)), ((-2, 3), (2, 3)), ((1, 4), (2, 3)), ((1, 4), (4, 6))]
  
      Raises
      ------
      :exc:`TypeError`
          if `intervals` contains None or an element which is not
          collections.abc.Sequence or not a length of 2.
      :exc:`ValueError`
          if `intervals` contains an interval such that min1 > max1
          where min1,max1 = interval
      """
      intervals = list(intervals)
      for interval in intervals:
          if not (
              isinstance(interval, Sequence) and len(interval) == 2
          ):
              raise TypeError(
                  "Each interval must have length 2, and be a "
                  "collections.abc.Sequence such as tuple or list."
              )
          if interval[0] > interval[1]:
              raise ValueError(
                  f"Interval must have lower value first. Got {interval}"
              )
  
      graph = nx.Graph()
  
      tupled_intervals = [tuple(interval) for interval in intervals]
      graph.add_nodes_from(tupled_intervals)
  
      while tupled_intervals:
          min1, max1 = interval1 = tupled_intervals.pop()
          for interval2 in tupled_intervals:
              min2, max2 = interval2
              if max1 >= min2 and max2 >= min1:
                  graph.add_edge(interval1, interval2)
      return graph
  
label_desc: Use image node_id 1 for calling a global function with example usage: interval_graph(intervals) and returns: graph