old_contents: class Instance(object):
  
      def __init__(self, latency, eeg_data, frequency):
          self.latency = latency
          self.eeg_data = eeg_data
          self.frequency = frequency
new_contents: class Instance(object):
  
      def __init__(self, patient_id, latencies, eeg_data, sample_rate):
          self.patient_id = patient_id
          self.latencies = latencies
          self.eeg_data = eeg_data
          self.sample_rate = sample_rate
subject: Add patient_id.