code: def _concat(self, data):
          
          if isinstance(data, np.ndarray):
              data_length = len(data)
              if data_length < self.length:
                  prev_chunk = self.data[-(self.length-data_length):]
                  data = np.concatenate([prev_chunk, data])
              elif data_length > self.length:
                  data = data[-self.length:]
          elif util.pd and isinstance(data, util.pd.DataFrame):
              data_length = len(data)
              if data_length < self.length:
                  prev_chunk = self.data.iloc[-(self.length-data_length):]
                  data = util.pd.concat([prev_chunk, data])
              elif data_length > self.length:
                  data = data.iloc[-self.length:]
          elif isinstance(data, dict) and data:
              data_length = len(list(data.values())[0])
              new_data = {}
              for k, v in data.items():
                  if data_length < self.length:
                      prev_chunk = self.data[k][-(self.length-data_length):]
                      new_data[k] = np.concatenate([prev_chunk, v])
                  elif data_length > self.length:
                      new_data[k] = v[-self.length:]
                  else:
                      new_data[k] = v
              data = new_data
          self._chunk_length = data_length
          return data
docs: Concatenate and slice the accepted data types to the defined
          length.