class_docstr: Sequential execution
class_docstr_tok: ["Sequential","execution"]
code: def __init__(self, comm, ng=1, tag=0):
      ng = int(ng)
      tag = int(tag)
      assert ng >= 1
      assert ng <= comm.Get_size()
      self.comm = comm
      self.ng = ng
      self.tag = tag
  
label_desc: Use image node_id 1 to create a new Seq object  with example: obj = Seq(comm, ng, tag)