code: def print_statistics(self):
      print("n_users=%d, n_items=%d" % (self.n_users, self.n_items))
      print("n_interactions=%d" % (self.n_train + self.n_test))
      print(
          "n_train=%d, n_test=%d, sparsity=%.5f"
          % (
              self.n_train,
              self.n_test,
              (self.n_train + self.n_test)
              / (self.n_users * self.n_items),
          )
      )
  
file_path: dgl/examples/pytorch/NGCF/NGCF/utility/load_data.py
imports: import random
  import dgl
  import numpy
label_desc: Use image node_id 4 for calling the Data obj's underlying member method code with example usage: obj.print_statistics() without return types