unfurl

# File activestorage/app/models/active_storage/blob.rb, line 249
  def unfurl(io, identify: true) # :nodoc:
    self.checksum     = compute_checksum_in_chunks(io)
    self.content_type = extract_content_type(io) if content_type.nil? || identify
    self.byte_size    = io.size
    self.identified   = true
  end