fixed flake8 errors

torch_cluster/radius.py

 from typing import Optional
 
 import torch
-import scipy.spatial
-
 
 @torch.jit.script
 def sample(col: torch.Tensor, count: int) -> torch.Tensor:
@@ -87,7 +85,6 @@ def radius(x: torch.Tensor, y: torch.Tensor, r: float,
         assert x.size(0) == batch_x.size(0)
         assert y.size(0) == batch_y.size(0)
 
-        
         x = torch.cat([x, 2 * r * batch_x.view(-1, 1).to(x.dtype)], dim=-1)
         y = torch.cat([y, 2 * r * batch_y.view(-1, 1).to(y.dtype)], dim=-1)
 
@@ -104,6 +101,7 @@ def radius(x: torch.Tensor, y: torch.Tensor, r: float,
         return torch.stack([row[mask], col[mask]], dim=0)
         """
 
+
 def radius_graph(x: torch.Tensor, r: float,
                  batch: Optional[torch.Tensor] = None, loop: bool = False,
                  max_num_neighbors: int = 32,
@@ -144,7 +142,7 @@ def radius_graph(x: torch.Tensor, r: float,
         row, col = (col, row) if flow == 'source_to_target' else (row, col)
     else:
         row, col = (col, row) if flow == 'target_to_source' else (row, col)
-        
+
     if not loop:
         mask = row != col
         row, col = row[mask], col[mask]