old_contents: # Copyright 2014 Donald Stufft
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  # http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  from __future__ import absolute_import, division, print_function
  
  import bleach
  
  
  ALLOWED_TAGS = [
      # Bleach Defaults
      "a", "abbr", "acronym", "b", "blockquote", "code", "em", "i", "li", "ol",
      "strong", "ul",
  
      # Custom Additions
      "br", "cite", "col", "colgroup", "dd", "div", "dl", "dt", "h1", "h2", "h3",
      "h4", "h5", "h6", "hr", "img", "p", "pre", "span", "table", "tbody", "td",
      "th", "thead", "tr", "tt", "kbd", "var",
  ]
  
  ALLOWED_ATTRIBUTES = {
      # Bleach Defaults
      "a": ["href", "title"],
      "abbr": ["title"],
      "acronym": ["title"],
  
      # Custom Additions
      "*": ["id"],
      "hr": ["class"],
      "img": ["src"],
      "span": ["class"],
  }
  
  ALLOWED_STYLES = []
  
  
  def clean(html, tags=None, attributes=None, styles=None):
      if tags is None:
          tags = ALLOWED_TAGS
      if attributes is None:
          attributes = ALLOWED_ATTRIBUTES
      if styles is None:
          styles = ALLOWED_STYLES
  
      def nofollow(attrs, new=False):
          if attrs["href"].startswith("mailto:"):
              return attrs
          attrs["rel"] = "nofollow"
          return attrs
  
      # Clean the output using Bleach
      cleaned = bleach.clean(
          html,
          tags=tags,
          attributes=attributes,
          styles=styles,
      )
  
      # Bleach Linkify makes it easy to modify links, however, we will not be
      # using it to create additional links.
      cleaned = bleach.linkify(
          cleaned,
          callbacks=[
              lambda attrs, new: attrs if not new else None,
              nofollow,
          ],
          skip_pre=True,
          parse_email=False,
      )
  
      return cleaned
  
new_contents: # Copyright 2014 Donald Stufft
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  # http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  from __future__ import absolute_import, division, print_function
  
  import bleach
  
  
  ALLOWED_TAGS = [
      # Bleach Defaults
      "a", "abbr", "acronym", "b", "blockquote", "code", "em", "i", "li", "ol",
      "strong", "ul",
  
      # Custom Additions
      "br", "cite", "col", "colgroup", "dd", "div", "dl", "dt", "h1", "h2", "h3",
      "h4", "h5", "h6", "hr", "img", "p", "pre", "span", "sub", "sup", "table",
      "tbody", "td", "th", "thead", "tr", "tt", "kbd", "var",
  ]
  
  ALLOWED_ATTRIBUTES = {
      # Bleach Defaults
      "a": ["href", "title"],
      "abbr": ["title"],
      "acronym": ["title"],
  
      # Custom Additions
      "*": ["id"],
      "hr": ["class"],
      "img": ["src"],
      "span": ["class"],
  }
  
  ALLOWED_STYLES = []
  
  
  def clean(html, tags=None, attributes=None, styles=None):
      if tags is None:
          tags = ALLOWED_TAGS
      if attributes is None:
          attributes = ALLOWED_ATTRIBUTES
      if styles is None:
          styles = ALLOWED_STYLES
  
      def nofollow(attrs, new=False):
          if attrs["href"].startswith("mailto:"):
              return attrs
          attrs["rel"] = "nofollow"
          return attrs
  
      # Clean the output using Bleach
      cleaned = bleach.clean(
          html,
          tags=tags,
          attributes=attributes,
          styles=styles,
      )
  
      # Bleach Linkify makes it easy to modify links, however, we will not be
      # using it to create additional links.
      cleaned = bleach.linkify(
          cleaned,
          callbacks=[
              lambda attrs, new: attrs if not new else None,
              nofollow,
          ],
          skip_pre=True,
          parse_email=False,
      )
  
      return cleaned
  
subject: Allow <sub> and <sup> tags