# LibTmux.Query.ToOne

- **Package:** libtmux-haskell
- **Language:** Haskell
- **Kind:** data type
- **Source:** https://github.com/libtmux/libtmux-haskell/blob/663e212622a02aa74a9bdc8ff71e2b45fcb1d4d5/internal/LibTmux/Internal/Query.hs#L63
- **Page:** https://libtmux.org/en/haskell/latest/reference/libtmux-query-t-toone/

```haskell
data ToOne parent child
```

A required relationship in a validated graph, used with [`related`](/en/haskell/latest/reference/libtmux-query-v-related/).