code: func NewBlobFieldDescriptor(nullable NullableColumn, metadata []byte) (
  	fd FieldDescriptor,
  	remaining []byte,
  	err error) {
  
  	if len(metadata) < 1 {
  		return nil, nil, errors.New("Metadata has too few bytes")
  	}
  
  	packedLen := LittleEndian.Uint8(metadata)
  
  	if packedLen > 4 {
  		return nil, nil, errors.New("Invalid packed length")
  	}
  
  	return &blobFieldDescriptor{
  		packedLengthFieldDescriptor: packedLengthFieldDescriptor{
  			baseFieldDescriptor: baseFieldDescriptor{
  				fieldType:  mysql_proto.FieldType_BLOB,
  				isNullable: nullable,
  			},
  			packedLength: int(packedLen),
  		},
  	}, metadata[1:], nil
  }
docs: // This returns a field descriptor for FieldType_BLOB (i.e., Field_blob)