old_contents: """
  Warnings (:mod:`skbio.core.warning`)
  ====================================
  
  .. currentmodule:: skbio.core.warning
  
  This module defines custom warning classes used throughout the core scikit-bio
  codebase.
  
  Warnings
  --------
  
  .. autosummary::
     :toctree: generated/
  
     EfficiencyWarning
  
  """
  
  # ----------------------------------------------------------------------------
  # Copyright (c) 2013--, scikit-bio development team.
  #
  # Distributed under the terms of the Modified BSD License.
  #
  # The full license is in the file COPYING.txt, distributed with this software.
  # ----------------------------------------------------------------------------
  
  from __future__ import absolute_import, division, print_function
  
  
  class EfficiencyWarning(Warning):
      pass
  
new_contents: """
  Warnings (:mod:`skbio.core.warning`)
  ====================================
  
  .. currentmodule:: skbio.core.warning
  
  This module defines custom warning classes used throughout the core scikit-bio
  codebase.
  
  Warnings
  --------
  
  .. autosummary::
     :toctree: generated/
  
     EfficiencyWarning
  
  """
  
  # ----------------------------------------------------------------------------
  # Copyright (c) 2013--, scikit-bio development team.
  #
  # Distributed under the terms of the Modified BSD License.
  #
  # The full license is in the file COPYING.txt, distributed with this software.
  # ----------------------------------------------------------------------------
  
  from __future__ import absolute_import, division, print_function
  
  
  class EfficiencyWarning(Warning):
      """Warn about potentially accidental use of inefficient code.
  
      For example, if a user doesn't have an optimized version of a
      function/algorithm available in their scikit-bio installation, a slower,
      pure-Python implementation may be used instead. This warning can be used to
      let the user know they are using a version of the function that could be
      potentially orders of magnitude slower.
  
      """
      pass
  
subject: Add docstring to EfficiencyWarning