## ChatMessage
### Definition
```protobuf
package library.rpc;
message ChatMessage {
string user_id = 1;
string text = 2;
int64 timestamp = 3;
}
```
### Dependencies
*None*
---
## CheckoutRequest
### Definition
```protobuf
package library.rpc;
message CheckoutRequest {
string isbn = 1;
}
```
### Dependencies
*None*
---
## CheckoutResponse
### Definition
```protobuf
package library.rpc;
message CheckoutResponse {
repeated library.domain.Book checked_out_books = 1;
int32 total_items = 2;
string due_date = 3;
}
```
### Dependencies
- Field `checked_out_books`: [Book](library.domain.md#Book)
---
## GetBookRequest
### Definition
```protobuf
package library.rpc;
message GetBookRequest {
string isbn = 1;
}
```
### Dependencies
*None*
---
## QueryBooksRequest
### Definition
```protobuf
package library.rpc;
message QueryBooksRequest {
string title_prefix = 1;
library.domain.Genre genre_filter = 2;
}
```
### Dependencies
- Field `genre_filter`: [Genre](library.domain.md#Genre)
---