old_contents: from dal import autocomplete
  from django import forms
  
  
  class BikeModelForm(forms.ModelForm):
      def __init__(self, *args, **kw):
          super(BikeModelForm, self).__init__(*args, **kw)
          if self.instance is not None:
              # Saved instance is loaded, setup choices to display the selected value
              self.fields['id_station'].widget.choices = ((self.instance.id_station, self.instance.station),)
  
      def validate_unique(self):
          super(BikeModelForm, self).validate_unique()
          if self.errors and 'id_station' in self.data:
              # A station was chosen, reinit choices with it
              self.fields['id_station'].widget.choices = ((self.cleaned_data['id_station'], self.data['station']),)
  
      class Meta:
          widgets = {
              'id_station': autocomplete.ListSelect2(url='station-autocomplete',
                                                     forward=('provider',),
                                                     attrs={'data-allow-clear': 'false'})
          }
  
      class Media:
          js = ('js/admin_form.js',)
  
new_contents: from dal import autocomplete
  from django import forms
  
  
  class BikeModelForm(forms.ModelForm):
      def __init__(self, *args, **kw):
          super(BikeModelForm, self).__init__(*args, **kw)
          if self.instance is not None:
              # Saved instance is loaded, setup choices to display the selected value
              self.fields['id_station'].widget.choices = ((self.instance.id_station, self.instance.station),)
  
      def validate_unique(self):
          """If the form had an error and a station was chosen, we need to setup the widget choices to the previously selected value for the autocomplete to display it properly"""
          super(BikeModelForm, self).validate_unique()
          if self.errors and 'id_station' in self.data:
              self.fields['id_station'].widget.choices = ((self.cleaned_data['id_station'], self.data['station']),)
  
      class Meta:
          widgets = {
              'id_station': autocomplete.ListSelect2(url='station-autocomplete',
                                                     forward=('provider',),
                                                     attrs={'data-allow-clear': 'false'})
          }
  
      class Media:
          js = ('js/admin_form.js',)
  
subject: Add docstring to explain the code