code: def concurrent_bfs(Graphs, sources, depth_limit=None, offload=False):
      """
      Find the breadth first traversals of multiple graphs with multiple sources
      in each graph.
  
      Parameters
      ----------
      Graphs : list of cugraph.Graph
          The adjacency lists will be computed if not already present.
  
      sources : list of cudf.Series
          For each graph, subset of vertices from which the traversals start.
          A BFS is run in Graphs[i] for each source in the Series at sources[i].
          The size of this list must match the size of the graph list.
          The size of each Series (ie. the number of sources per graph)
          is flexible, but cannot exceed the size of the corresponding graph.
  
  
      depth_limit : Integer, optional, default=None
          Limit the depth of the search. Terminates if no more vertices are
          reachable within the distance of depth_limit
  
      offload : boolean, optional, default=False
          Indicates if output should be written to the disk.
          When not provided, the algorithms decides if offloading is needed
          based on the input parameters.
  
      Returns
      -------
      Return type is decided based on the input parameters (size of
      sources, size of the graph, number of graphs and offload setting)
  
      If G is a cugraph.Graph and output fits in memory:
          BFS_edge_lists : cudf.DataFrame
              GPU data frame containing all BFS edges
          source_offsets: cudf.Series
              Series containing the starting offset in the returned edge list
              for each source.
  
      If offload is True, or if the output does not fit in memory :
          Writes csv files containing BFS output to the disk.
      """
      raise NotImplementedError(
          "concurrent_bfs is coming soon! Please up vote the github issue 1465\
               to help us prioritize"
      )
      if not isinstance(Graphs, list):
          raise TypeError("Graphs should be a list of cugraph.Graph")
      if not isinstance(sources, list):
          raise TypeError("sources should be a list of cudf.Series")
      if len(Graphs) != len(sources):
          raise ValueError(
              "The size of the sources list must match\
               the size of the graph list."
          )
      if offload is True:
          raise NotImplementedError(
              "Offloading is coming soon! Please up vote the github issue 1461\
               to help us prioritize"
          )
  
imports: import numpy
  import cudf
  import warnings
label_desc: Use image node_id 2 for calling a global function with example usage: concurrent_bfs(Graphs, sources, depth_limit, offload) without return types