prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  Problems when displaying multiple views of ContainerWidget. 
  `ContainerView.render` registers anonymous functions to `this.model.on('displayed')` . This is a problem because when rendering multiple views of the same widget container, multiple instances of this anonymous function get registered to this event. 
  
  PS: This is also related to #5958
  
  
  </issue>
  <code>
  [start of IPython/html/widgets/widget_container.py]
  1 """ContainerWidget class.  
  2 
  3 Represents a container that can be used to group other widgets.
  4 """
  5 #-----------------------------------------------------------------------------
  6 # Copyright (c) 2013, the IPython Development Team.
  7 #
  8 # Distributed under the terms of the Modified BSD License.
  9 #
  10 # The full license is in the file COPYING.txt, distributed with this software.
  11 #-----------------------------------------------------------------------------
  12 
  13 #-----------------------------------------------------------------------------
  14 # Imports
  15 #-----------------------------------------------------------------------------
  16 from .widget import DOMWidget
  17 from IPython.utils.traitlets import Unicode, Tuple, TraitError
  18 
  19 #-----------------------------------------------------------------------------
  20 # Classes
  21 #-----------------------------------------------------------------------------
  22 
  23 class ContainerWidget(DOMWidget):
  24     _view_name = Unicode('ContainerView', sync=True)
  25 
  26     # Child widgets in the container.
  27     # Using a tuple here to force reassignment to update the list.
  28     # When a proper notifying-list trait exists, that is what should be used here.
  29     children = Tuple()
  30     _children = Tuple(sync=True)
  31 
  32 
  33     def __init__(self, **kwargs):
  34         super(ContainerWidget, self).__init__(**kwargs)
  35         self.on_displayed(ContainerWidget._fire_children_displayed)
  36 
  37     def _fire_children_displayed(self):
  38         for child in self._children:
  39             child._handle_displayed()
  40 
  41     def _children_changed(self, name, old, new):
  42         """Validate children list.
  43 
  44         Makes sure only one instance of any given model can exist in the 
  45         children list.
  46         An excellent post on uniqifiers is available at 
  47             http://www.peterbe.com/plog/uniqifiers-benchmark
  48         which provides the inspiration for using this implementation.  Below
  49         I've implemented the `f5` algorithm using Python comprehensions."""
  50         if new is not None:
  51             seen = {}
  52             def add_item(i):
  53                 seen[i.model_id] = True
  54                 return i
  55             self._children = [add_item(i) for i in new if not i.model_id in seen]
  56 
  57 
  58 class PopupWidget(ContainerWidget):
  59     _view_name = Unicode('PopupView', sync=True)
  60     
  61     description = Unicode(sync=True)
  62     button_text = Unicode(sync=True)
  63
  [end of IPython/html/widgets/widget_container.py]
  </code>
  
  I need you to solve this issue by generating a single patch file that I can apply directly to this repository using git apply. Please respond with a single patch file in the following format.
  <patch>
  diff --git a/file.py b/file.py
  --- a/file.py
  +++ b/file.py
  @@ -1,27 +1,35 @@
   def euclidean(a, b):
  -    while b:
  -        a, b = b, a % b
  -    return a
  +    if b == 0:
  +        return a
  +    return euclidean(b, a % b)
   
   
   def bresenham(x0, y0, x1, y1):
       points = []
       dx = abs(x1 - x0)
       dy = abs(y1 - y0)
  -    sx = 1 if x0 < x1 else -1
  -    sy = 1 if y0 < y1 else -1
  -    err = dx - dy
  +    x, y = x0, y0
  +    sx = -1 if x0 > x1 else 1
  +    sy = -1 if y0 > y1 else 1
   
  -    while True:
  -        points.append((x0, y0))
  -        if x0 == x1 and y0 == y1:
  -            break
  -        e2 = 2 * err
  -        if e2 > -dy:
  -            err -= dy
  -            x0 += sx
  -        if e2 < dx:
  -            err += dx
  -            y0 += sy
  +    if dx > dy:
  +        err = dx / 2.0
  +        while x != x1:
  +            points.append((x, y))
  +            err -= dy
  +            if err < 0:
  +                y += sy
  +                err += dx
  +            x += sx
  +    else:
  +        err = dy / 2.0
  +        while y != y1:
  +            points.append((x, y))
  +            err -= dx
  +            if err < 0:
  +                x += sx
  +                err += dy
  +            y += sy
  +
  +    points.append((x, y))
       return points
  
  </patch>
golden_diff: diff --git a/IPython/html/widgets/widget_container.py b/IPython/html/widgets/widget_container.py
  --- a/IPython/html/widgets/widget_container.py
  +++ b/IPython/html/widgets/widget_container.py
  @@ -2,58 +2,29 @@
   
   Represents a container that can be used to group other widgets.
   """
  -#-----------------------------------------------------------------------------
  -# Copyright (c) 2013, the IPython Development Team.
  -#
  +
  +# Copyright (c) IPython Development Team.
   # Distributed under the terms of the Modified BSD License.
  -#
  -# The full license is in the file COPYING.txt, distributed with this software.
  -#-----------------------------------------------------------------------------
   
  -#-----------------------------------------------------------------------------
  -# Imports
  -#-----------------------------------------------------------------------------
   from .widget import DOMWidget
   from IPython.utils.traitlets import Unicode, Tuple, TraitError
   
  -#-----------------------------------------------------------------------------
  -# Classes
  -#-----------------------------------------------------------------------------
  -
   class ContainerWidget(DOMWidget):
       _view_name = Unicode('ContainerView', sync=True)
   
       # Child widgets in the container.
       # Using a tuple here to force reassignment to update the list.
       # When a proper notifying-list trait exists, that is what should be used here.
  -    children = Tuple()
  -    _children = Tuple(sync=True)
  -
  +    children = Tuple(sync=True)
   
       def __init__(self, **kwargs):
           super(ContainerWidget, self).__init__(**kwargs)
           self.on_displayed(ContainerWidget._fire_children_displayed)
   
       def _fire_children_displayed(self):
  -        for child in self._children:
  +        for child in self.children:
               child._handle_displayed()
   
  -    def _children_changed(self, name, old, new):
  -        """Validate children list.
  -
  -        Makes sure only one instance of any given model can exist in the 
  -        children list.
  -        An excellent post on uniqifiers is available at 
  -            http://www.peterbe.com/plog/uniqifiers-benchmark
  -        which provides the inspiration for using this implementation.  Below
  -        I've implemented the `f5` algorithm using Python comprehensions."""
  -        if new is not None:
  -            seen = {}
  -            def add_item(i):
  -                seen[i.model_id] = True
  -                return i
  -            self._children = [add_item(i) for i in new if not i.model_id in seen]
  -
   
   class PopupWidget(ContainerWidget):
       _view_name = Unicode('PopupView', sync=True)
  
verification_info: {"golden_diff": "diff --git a/IPython/html/widgets/widget_container.py b/IPython/html/widgets/widget_container.py\n--- a/IPython/html/widgets/widget_container.py\n+++ b/IPython/html/widgets/widget_container.py\n@@ -2,58 +2,29 @@\n \n Represents a container that can be used to group other widgets.\n \"\"\"\n-#-----------------------------------------------------------------------------\n-# Copyright (c) 2013, the IPython Development Team.\n-#\n+\n+# Copyright (c) IPython Development Team.\n # Distributed under the terms of the Modified BSD License.\n-#\n-# The full license is in the file COPYING.txt, distributed with this software.\n-#-----------------------------------------------------------------------------\n \n-#-----------------------------------------------------------------------------\n-# Imports\n-#-----------------------------------------------------------------------------\n from .widget import DOMWidget\n from IPython.utils.traitlets import Unicode, Tuple, TraitError\n \n-#-----------------------------------------------------------------------------\n-# Classes\n-#-----------------------------------------------------------------------------\n-\n class ContainerWidget(DOMWidget):\n     _view_name = Unicode('ContainerView', sync=True)\n \n     # Child widgets in the container.\n     # Using a tuple here to force reassignment to update the list.\n     # When a proper notifying-list trait exists, that is what should be used here.\n-    children = Tuple()\n-    _children = Tuple(sync=True)\n-\n+    children = Tuple(sync=True)\n \n     def __init__(self, **kwargs):\n         super(ContainerWidget, self).__init__(**kwargs)\n         self.on_displayed(ContainerWidget._fire_children_displayed)\n \n     def _fire_children_displayed(self):\n-        for child in self._children:\n+        for child in self.children:\n             child._handle_displayed()\n \n-    def _children_changed(self, name, old, new):\n-        \"\"\"Validate children list.\n-\n-        Makes sure only one instance of any given model can exist in the \n-        children list.\n-        An excellent post on uniqifiers is available at \n-            http://www.peterbe.com/plog/uniqifiers-benchmark\n-        which provides the inspiration for using this implementation.  Below\n-        I've implemented the `f5` algorithm using Python comprehensions.\"\"\"\n-        if new is not None:\n-            seen = {}\n-            def add_item(i):\n-                seen[i.model_id] = True\n-                return i\n-            self._children = [add_item(i) for i in new if not i.model_id in seen]\n-\n \n class PopupWidget(ContainerWidget):\n     _view_name = Unicode('PopupView', sync=True)\n", "issue": "Problems when displaying multiple views of ContainerWidget. \n`ContainerView.render` registers anonymous functions to `this.model.on('displayed')` . This is a problem because when rendering multiple views of the same widget container, multiple instances of this anonymous function get registered to this event. \n\nPS: This is also related to #5958\n\n", "before_files": [{"content": "\"\"\"ContainerWidget class.  \n\nRepresents a container that can be used to group other widgets.\n\"\"\"\n#-----------------------------------------------------------------------------\n# Copyright (c) 2013, the IPython Development Team.\n#\n# Distributed under the terms of the Modified BSD License.\n#\n# The full license is in the file COPYING.txt, distributed with this software.\n#-----------------------------------------------------------------------------\n\n#-----------------------------------------------------------------------------\n# Imports\n#-----------------------------------------------------------------------------\nfrom .widget import DOMWidget\nfrom IPython.utils.traitlets import Unicode, Tuple, TraitError\n\n#-----------------------------------------------------------------------------\n# Classes\n#-----------------------------------------------------------------------------\n\nclass ContainerWidget(DOMWidget):\n    _view_name = Unicode('ContainerView', sync=True)\n\n    # Child widgets in the container.\n    # Using a tuple here to force reassignment to update the list.\n    # When a proper notifying-list trait exists, that is what should be used here.\n    children = Tuple()\n    _children = Tuple(sync=True)\n\n\n    def __init__(self, **kwargs):\n        super(ContainerWidget, self).__init__(**kwargs)\n        self.on_displayed(ContainerWidget._fire_children_displayed)\n\n    def _fire_children_displayed(self):\n        for child in self._children:\n            child._handle_displayed()\n\n    def _children_changed(self, name, old, new):\n        \"\"\"Validate children list.\n\n        Makes sure only one instance of any given model can exist in the \n        children list.\n        An excellent post on uniqifiers is available at \n            http://www.peterbe.com/plog/uniqifiers-benchmark\n        which provides the inspiration for using this implementation.  Below\n        I've implemented the `f5` algorithm using Python comprehensions.\"\"\"\n        if new is not None:\n            seen = {}\n            def add_item(i):\n                seen[i.model_id] = True\n                return i\n            self._children = [add_item(i) for i in new if not i.model_id in seen]\n\n\nclass PopupWidget(ContainerWidget):\n    _view_name = Unicode('PopupView', sync=True)\n    \n    description = Unicode(sync=True)\n    button_text = Unicode(sync=True)\n", "path": "IPython/html/widgets/widget_container.py"}]}