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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def variable_device(device, name):
 """Fix the variable device to colocate its ops."""

  if callable(device):
    var_name = tf.get_variable_scope().name + '/' + name
    var_def = tf.NodeDef(name=var_name, op='Variable')
    device = device(var_def)
  if device is None:
    device = ''
  return device