title: create a mask given bounding box
body: <pre><code>arr = []
  j =0 
  for img in train['image_id'].unique():
      bbox = train[train['image_id'] == img]   #bbox[0] = x ,similarly others 
      template = np.zeros((1024,1024))
      j+=1
      for i in train.itertuples():
          template[i._6:i._6 + i._8  ,  i._7:i._7 + i._9] = 1 
      arr.append(template)
  </code></pre>
  <p>here i._6 , i._8 , i._7 , i._9
  are values of bounding boxes<br />
  Is there a way to make this code fast</p>