app\models.py

#...
import ast

class Content(db.Model):
  #...
  
  def to_json(self, video=True, iframe=True, audio=True)
        json_content = {
          'id': self.id,
          'title': self.title,
          'description': self.description,
          'lang': self.lang,
          'author': self.author,
          'publisher': self.publisher,
          'image': {'url': self.image_url,
                    'type': self.image_type,
                    'size': self.image_size,
                    'height': self.image_height,
                    'width': self.image_width,
                    'size_pretty': self.image_size_pretty},
          'date': self.date,
          'url': self.url,
          'logo': {'url': self.logo_url,
                   'type': self.logo_type,
                   'size': self.logo_size,
                   'height': self.logo_height,
                   'width': self.logo_width,
                   'size_pretty': self.logo_size_pretty},
          'audio': self.audio,
          'video': self.video,
          'iframe': self.iframe,
      }

      if audio:
          json_content['audio'] = {'url': self.audio_url,
                                   'type': self.audio_type,
                                   'duration': self.audio_duration,
                                   'size': self.audio_size,
                                   'duration_pretty': self.audio_duration_pretty,
                                   'size_pretty': self.audio_size_pretty,
                                    } if self.audio else self.audio
      if iframe:
          json_content['iframe'] = {'html': self.iframe_html,
                                    'scripts': ast.literal_eval(self.iframe_scripts) if self.iframe_scripts else []
                                    } if self.iframe else self.iframe
      if video:
          json_content['video'] = {'url': self.video_url,
                                   'type': self.video_type,
                                   'duration': self.video_duration,
                                   'size': self.video_size,
                                   'height': self.video_height,
                                   'width': self.video_width,
                                   'duration_pretty': self.video_duration_pretty,
                                   'size_pretty': self.video_size_pretty
                                   } if self.video else self.video,

      return json_content