Issue with fetching Mux video type in Sanity schema using Groq

{
  title: 'Content',
  name: 'content',
  type: 'array',
  of: [
    {
      type: 'block'
    }, {
      type: "mux.video"
    },
    {
      type: 'image',
      options: {
        hotspot: true
      },
      fields: [
        {
          name: 'caption',
          type: 'string',
          title: 'Caption',
          options: {
            isHighlighted: true // <-- make this field easily accessible
          }
        },
      ]

    }
  ]
},

"lesson": *[slug.current == $lessonSlug][0] { 
    _id,
    slug,
    title,
    content,
}

*_ref*: "1eaec214-7eac-4b97-95fa-b843fa4373b2"

content[] {
    ...,
    _type == "mux.video" => {
        asset->,
    },
}

const lesson = {
  name: 'lesson',
  title: 'Lesson',
  type: 'document',
  fields: [
    {
      title: 'Titel',
      name: 'title',
      type: 'string',
    },
    {
      title: 'Slug',
      name: 'slug',
      type: 'slug',
      options: {
        source: 'title',
        maxLength: 200, // will be ignored if slugify is set
        slugify: input => input
            .toLowerCase()
            .replace(/\s+/g, '-')
            .slice(0, 200)
      }
    },
    {
      title: 'Content',
      name: 'content',
      type: 'array',
      of: [
        {
          type: 'block'
        }, {
          type: "mux.video"
        },
        {
          type: 'image',
          options: {
            hotspot: true
          },
          fields: [
            {
              name: 'caption',
              type: 'string',
              title: 'Caption',
              options: {
                isHighlighted: true // <-- make this field easily accessible
              }
            },
          ]

        }
      ]
    },
  ]
}

export default lesson;