code: def get_prep_value(self, value):
          "Returns field's value prepared for saving into a database."
          value = self.get_clean_value(value)
          if self.multiple:
              if value:
                  value = ",".join(value)
              else:
                  value = ""
          return super(CharField, self).get_prep_value(valuef get_prep_value(self, value):
          "Returns field's value prepared for saving into a database."
          value = self.get_clean_value(value)
          if self.multiple:
              if value:
                  value = ",".join(value)
              else:
                  value = ""
          return super(CharField, self).get_prep_value(value)
docs: Returns field's value prepared for saving into a database.