old_contents: 
  # Copyright (c) 2016, The Bifrost Authors. All rights reserved.
  # Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  # * Redistributions of source code must retain the above copyright
  #   notice, this list of conditions and the following disclaimer.
  # * Redistributions in binary form must reproduce the above copyright
  #   notice, this list of conditions and the following disclaimer in the
  #   documentation and/or other materials provided with the distribution.
  # * Neither the name of The Bifrost Authors nor the names of its
  #   contributors may be used to endorse or promote products derived
  #   from this software without specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
  # EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  # PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  # CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  # PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  # PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  # OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  from __future__ import absolute_import
  
  from bifrost.pipeline import TransformBlock
  from bifrost.ndarray import copy_array
  
  from copy import deepcopy
  
  class CopyBlock(TransformBlock):
  	def __init__(self, iring, space=None, *args, **kwargs):
  		super(CopyBlock, self).__init__(iring, *args, **kwargs)
  		if space is None:
  			space = self.iring.space
  		self.orings = [self.create_ring(space=space)]
  	def on_sequence(self, iseq):
  		ohdr = deepcopy(iseq.header)
  		return ohdr
  	def on_data(self, ispan, ospan):
  		copy_array(ospan.data, ispan.data)
  
  def copy(iring, space=None, *args, **kwargs):
  	return CopyBlock(iring, space, *args, **kwargs)
  
new_contents: 
  # Copyright (c) 2016, The Bifrost Authors. All rights reserved.
  # Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  # * Redistributions of source code must retain the above copyright
  #   notice, this list of conditions and the following disclaimer.
  # * Redistributions in binary form must reproduce the above copyright
  #   notice, this list of conditions and the following disclaimer in the
  #   documentation and/or other materials provided with the distribution.
  # * Neither the name of The Bifrost Authors nor the names of its
  #   contributors may be used to endorse or promote products derived
  #   from this software without specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
  # EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  # PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  # CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  # PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  # PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  # OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  from __future__ import absolute_import
  
  from bifrost.pipeline import TransformBlock
  from bifrost.ndarray import copy_array
  
  from copy import deepcopy
  
  class CopyBlock(TransformBlock):
  	def __init__(self, iring, space=None, *args, **kwargs):
  		super(CopyBlock, self).__init__(iring, *args, **kwargs)
  		if space is None:
  			space = self.iring.space
  		self.orings = [self.create_ring(space=space)]
  	def on_sequence(self, iseq):
  		ohdr = deepcopy(iseq.header)
  		return ohdr
  	def on_data(self, ispan, ospan):
  		copy_array(ospan.data, ispan.data)
  
  def copy(iring, space=None, *args, **kwargs):
      """Copy the contents of a ring to another space.
  
      Use this block to copy data between different
          spaces, such as from system memory to GPU memory.
          The output header for this block is identical
          to the input header.
  
      Attributes
      ----------
      iring : Block
          A derivative of a Block object.
      space : str, optional
          String describing the output data space,
          such as 'cuda' or 'system'. Default
          space is same as input.
      *args
          Arguments to `bifrost.pipeline.TransformBlock`.
      **kwargs
          Keyword Arguments to `bifrost.pipeline.TransformBlock`.
  
      Returns
      -------
      `CopyBlock`
      """
  	return CopyBlock(iring, space, *args, **kwargs)
  
subject: Add docstrings