docstr: Convert the model to the noise prediction model or the data prediction model.
docstr_tok: ["Convert","the","model","to","the","noise","prediction","model","or","the","data","prediction","model","."]
code: def model_fn(self, x, t):
      """
      Convert the model to the noise prediction model or the data prediction model.
      """
      if self.predict_x0:
          return self.data_prediction_fn(x, t)
      else:
          return self.noise_prediction_fn(x, t)
  
imports: import math
  import torch
  from tqdm import tqdm
label_desc: Use image node_id 4 for calling the DPM_Solver obj's underlying member method code with example usage: obj.model_fn(x, t) and returns: self, self