new_contents: #   Copyright 2013 OpenStack Foundation
  #
  #   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.
  #
  
  """argparse Custom Actions"""
  
  import argparse
  
  
  class KeyValueAction(argparse.Action):
      """A custom action to parse arguments as key=value pairs.
      Ensures that dest is a dict
      """
      def __call__(self, parser, namespace, values, option_string=None):
          # Make sure we have an empty dict rather than None
          if getattr(namespace, self.dest, None) is None:
              setattr(namespace, self.dest, {})
  
          # Add value if an assignment else remove it
          if '=' in values:
              getattr(namespace, self.dest, {}).update([values.split('=', 1)])
          else:
              getattr(namespace, self.dest, {}).pop(values, None)
  
subject: Tweak volume commands and add k=v argparse action