```ruby
# Model for storing versions of nodes.

# Note that this version (currently only in the "mongo" branch) uses
# MongoDB and MongoMapper, rather than ActiveRecord.

class NodeVersion
  include MongoMapper::Document

  key :node_id, Integer, :index => true
  key :person_id, Integer, :index => true
  key :description, String, :index => true
  key :contents, String, :index => true
  timestamps!

  validates_presence_of :node_id
  validates_presence_of :person_id
  validates_presence_of :description
  validates_presence_of :contents

  after_save :update_model_modification_time

  SECTION_SEPARATOR = '@#$#@#$#@'

  def node
    node_id.nil? ? nil : Node.find(node_id)
  end

  def person
    person_id.nil? ? nil : Person.find(person_id)
  end

  def person=(a_person)
    person_id = a_person.id
    save!
  end

  def uploaded_body=(model_file)
    contents = model_file.read
  end

  def procedures_tab
    contents.split(SECTION_SEPARATOR)[0]
  end

  def info_tab
    contents.split(SECTION_SEPARATOR)[2]
  end

  def netlogo_version
    contents.split(SECTION_SEPARATOR)[4].gsub("\n", "").gsub("NetLogo ", "")
  end

  def procedures_content
    contents.split(SECTION_SEPARATOR)[0]
  end

  def info_content
    contents.split(SECTION_SEPARATOR)[2]
  end

  # Callbacks

  def update_model_modification_time
    node.update_attributes(:updated_at => Time.now)
  end

end
```

Remove index from long string
user
```ruby
# Model for storing versions of nodes.

# Note that this version (currently only in the "mongo" branch) uses
# MongoDB and MongoMapper, rather than ActiveRecord.

class NodeVersion
  include MongoMapper::Document

  key :node_id, Integer, :index => true
  key :person_id, Integer, :index => true
  key :description, String, :index => true
  key :contents, String
  timestamps!

  validates_presence_of :node_id
  validates_presence_of :person_id
  validates_presence_of :description
  validates_presence_of :contents

  after_save :update_model_modification_time

  SECTION_SEPARATOR = '@#$#@#$#@'

  def node
    node_id.nil? ? nil : Node.find(node_id)
  end

  def person
    person_id.nil? ? nil : Person.find(person_id)
  end

  def person=(a_person)
    person_id = a_person.id
    save!
  end

  def uploaded_body=(model_file)
    contents = model_file.read
  end

  def procedures_tab
    contents.split(SECTION_SEPARATOR)[0]
  end

  def info_tab
    contents.split(SECTION_SEPARATOR)[2]
  end

  def netlogo_version
    contents.split(SECTION_SEPARATOR)[4].gsub("\n", "").gsub("NetLogo ", "")
  end

  def procedures_content
    contents.split(SECTION_SEPARATOR)[0]
  end

  def info_content
    contents.split(SECTION_SEPARATOR)[2]
  end

  # Callbacks

  def update_model_modification_time
    node.update_attributes(:updated_at => Time.now)
  end

end
```
assistant