code: def computeoffset(self, net):
      self.reset(net)
      offsets = net.ComputeOffset(
          [self.cursor] + self.dataset.content().field_blobs(),
          "offsets",
      )
      self.offsets = offsets
  
imports: from caffe2.python import core, workspace
  from caffe2.python.dataio import Reader, Writer
  from caffe2.python.schema import Struct, from_blob_list, from_column_list, InitEmptyRecord
  import numpy
label_desc: Use image node_id 4 for calling the _DatasetRandomReader obj's underlying member method code with example usage: obj.computeoffset(net) without return types