title: Object of type 'method' has no len() when define a class
body: <h2>I defined a class</h2>
  <pre><code>class Potsdam_Microgrid_DS1(Dataset):
      def __init__(self, root, transform=None, pre_transform=None):
          super().__init__(root, transform, pre_transform)
  
      #List all processed data 
      def processed_file_names(self):
          return ['data_1.pt', 'data_2.pt', 'data_3.pt']
       
      def len(self):
          return len(self.processed_file_names)
  
      def get(self, idx):
          data = torch.load(osp.join(self.processed_dir, 'data_{}.pt'.format(idx)))
          return data
  </code></pre>
  <hr />
  <h2>Then run</h2>
  <pre><code>Dataset_path = 'C:\\Users\\SPSC\\Documents\\Potsdam IMGData\\data'
  Data=Potsdam_Microgrid_DS1(Dataset_path)
  Data.len()
  </code></pre>
  <hr />
  <h2>Results</h2>
  <pre><code>    TypeError                                 Traceback (most recent call last)
  ~\AppData\Local\Temp\3/ipykernel_29288/1760764674.py in &lt;module&gt;
  ----&gt; 1 Data.len()
  
  ~\AppData\Local\Temp\3/ipykernel_29288/3878533142.py in len(self)
        8 
        9     def len(self):
  ---&gt; 10         return len(self.processed_file_names)
       11 
       12     def get(self, idx):
  
  TypeError: object of type 'method' has no len()
  </code></pre>
  <hr />
  <p>I have no ideas why.</p>