docs: def verify(path):
          """Verify that `path` has the qpimage series file format"""
          valid = False
          try:
              h5 = h5py.File(path, mode="r")
              qpi0 = h5["qpi_0"]
          except (OSError, KeyError):
              pass
          else:
              if ("qpimage version" in qpi0.attrs and
                  "phase" in qpi0 and
                  "amplitude" in qpi0 and
                  "bg_data" in qpi0["phase"] and
                      "bg_data" in qpi0["amplitude"]):
                  valid = True
          return valid