text: # Copyright (C) 2003-2005 Peter J. Verveer
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  #
  # 1. Redistributions of source code must retain the above copyright
  #    notice, this list of conditions and the following disclaimer.
  #
  # 2. 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.
  #
  # 3. The name of the author may not be used to endorse or promote
  #    products derived from this software without specific prior
  #    written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 collections.abc import Iterable
  import numpy
  
  
  def _extend_mode_to_code(mode):
      """Convert an extension mode to the corresponding integer code.
      """
      if mode == 'nearest':
          return 0
      elif mode == 'wrap':
          return 1
      elif mode == 'reflect':
          return 2
      elif mode == 'mirror':
          return 3
      elif mode == 'constant':
          return 4
      else:
          raise RuntimeError('boundary mode not supported')
  
  
  def _normalize_sequence(input, rank):
      """If input is a scalar, create a sequence of length equal to the
      rank by duplicating the input. If input is a sequence,
      check if its length is equal to the length of array.
      """
      is_str = isinstance(input, str)
      if not is_str and isinstance(input, Iterable):
          normalized = list(input)
          if len(normalized) != rank:
              err = "sequence argument must have length equal to input rank"
              raise RuntimeError(err)
      else:
          normalized = [input] * rank
      return normalized
  
  
  def _get_output(output, input, shape=None):
      if shape is None:
          shape = input.shape
      if output is None:
          output = numpy.zeros(shape, dtype=input.dtype.name)
      elif isinstance(output, (type, numpy.dtype)):
          # Classes (like `np.float32`) and dtypes are interpreted as dtype
          output = numpy.zeros(shape, dtype=output)
      elif isinstance(output, str):
          output = numpy.typeDict[output]
          output = numpy.zeros(shape, dtype=output)
      elif output.shape != shape:
          raise RuntimeError("output shape not correct")
      return output
  