self.fields["presentation"] = self.build_presentation_field()

        else:

            self.fields["content_override"] = self.build_content_override_field()

    def build_presentation_field(self):

        kwargs = {}

        queryset = Presentation.objects.all()

        queryset = queryset.exclude(cancelled=True)

        queryset = queryset.order_by("proposal_base__pk")

        if self.slot.content:

            queryset = queryset.filter(Q(slot=None) | Q(pk=self.slot.content.pk))

            kwargs["required"] = False

            kwargs["initial"] = self.slot.content

        else:

            queryset = queryset.filter(slot=None)

            kwargs["required"] = True

        kwargs["queryset"] = queryset

        return forms.ModelChoiceField(**kwargs)

    def build_content_override_field(self):

        kwargs = {

            "label": "Content",

            "required": False,

            "initial": self.slot.content_override,

        }

        return forms.CharField(**kwargs)

class ScheduleSectionForm(forms.Form):

    required_css_class = 'label-required'

    ROOM_KEY = 'room'

    DATE_KEY = 'date'

    START_KEY = 'time_start'

    END_KEY = 'time_end'

    EXCLUSIVE = 'exclusive'

    PROPOSAL = 'proposal_id'

    KIND = 'kind'

    filename = forms.FileField(

        label='Select a CSV file to import:',

        required=False

    )

    def __init__(self, *args, **kwargs):

        self.schedule = kwargs.pop("schedule")

        if 'encoding' in kwargs: