new_contents: #    Copyright 2013 IBM Corp.
  #
  #    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.
  
  """Utility methods for objects"""
  
  import ast
  import datetime
  
  import iso8601
  import netaddr
  from oslo.utils import timeutils
  import six
  
  from magnum.openstack.common._i18n import _
  
  
  def datetime_or_none(dt):
      """Validate a datetime or None value."""
      if dt is None:
          return None
      elif isinstance(dt, datetime.datetime):
          if dt.utcoffset() is None:
              # NOTE(danms): Legacy objects from sqlalchemy are stored in UTC,
              # but are returned without a timezone attached.
              # As a transitional aid, assume a tz-naive object is in UTC.
              return dt.replace(tzinfo=iso8601.iso8601.Utc())
          else:
              return dt
      raise ValueError(_("A datetime.datetime is required here"))
  
  
  def datetime_or_str_or_none(val):
      if isinstance(val, six.string_types):
          return timeutils.parse_isotime(val)
      return datetime_or_none(val)
  
  
  def int_or_none(val):
      """Attempt to parse an integer value, or None."""
      if val is None:
          return val
      else:
          return int(val)
  
  
  def str_or_none(val):
      """Attempt to stringify a value to unicode, or None."""
      if val is None:
          return val
      else:
          return six.text_type(val)
  
  
  def dict_or_none(val):
      """Attempt to dictify a value, or None."""
      if val is None:
          return {}
      elif isinstance(val, six.string_types):
          return dict(ast.literal_eval(val))
      else:
          try:
              return dict(val)
          except ValueError:
              return {}
  
  
  def list_or_none(val):
      """Attempt to listify a value, or None."""
      if val is None:
          return []
      elif isinstance(val, six.string_types):
          return list(ast.literal_eval(val))
      else:
          try:
              return list(val)
          except ValueError:
              return []
  
  
  def ip_or_none(version):
      """Return a version-specific IP address validator."""
      def validator(val, version=version):
          if val is None:
              return val
          else:
              return netaddr.IPAddress(val, version=version)
      return validator
  
  
  def nested_object_or_none(objclass):
      def validator(val, objclass=objclass):
          if val is None or isinstance(val, objclass):
              return val
          raise ValueError(_("An object of class %s is required here")
                           % objclass)
      return validator
  
  
  def dt_serializer(name):
      """Return a datetime serializer for a named attribute."""
      def serializer(self, name=name):
          if getattr(self, name) is not None:
              return timeutils.isotime(getattr(self, name))
          else:
              return None
      return serializer
  
  
  def dt_deserializer(instance, val):
      """A deserializer method for datetime attributes."""
      if val is None:
          return None
      else:
          return timeutils.parse_isotime(val)
  
  
  def obj_serializer(name):
      def serializer(self, name=name):
          if getattr(self, name) is not None:
              return getattr(self, name).obj_to_primitive()
          else:
              return None
      return serializer
  
subject: Add objects/utils.py copied from Ironic