old_contents: module.exports = {
    date: {
      type: Date,
      index: true
    },
    instagram_id: {
      type: String,
      index: true,
      unique: true
    },
    type: String,
    filter: String,
    tags: [String],
    caption: String,
    link: String,
    created_time: String,
    user: {
      username: String,
      profile_picture: String,
      id: String,
      full_name: String
    },
    images: {
      low_resolution: {
        url: String,
        width: Number,
        height: Number
      },
      thumbnail: {
        url: String,
        width: Number,
        height: Number
      },
      standard_resolution: {
        url: String,
        width: Number,
        height: Number
      }
    }
  };
  
new_contents: module.exports = {
    date: {
      type: Date,
      index: true
    },
    instagram_id: {
      type: String,
      index: true,
      unique: true
    },
    type: String,
    filter: String,
    tags: [String],
    caption: String,
    link: String,
    created_time: String,
    user: {
      username: String,
      profile_picture: String,
      id: String,
      full_name: String
    },
    images: {
      low_resolution: {
        url: String,
        width: Number,
        height: Number
      },
      thumbnail: {
        url: String,
        width: Number,
        height: Number
      },
      standard_resolution: {
        url: { type: String, index: true },
        width: Number,
        height: Number
      }
    }
  };
  
subject: index image urls