pub fn field<F>(f: F) -> Self
    where
        F: (Fn(&mut T) -> &mut dyn Prop) + Send + Sync + 'static,
    {
        Self::Field(Box::new(f) as Box<dyn (Fn(&mut T) -> &mut dyn Prop) + Send + Sync>)
    }
Creates a field property.

# Parameters

* `f` - The function used to get a mutable reference to the property.

# Examples

```no_run
# use ext_php_rs::props::Property;
struct Test {
pub a: i32,
}

let prop: Property<Test> = Property::field(|test: &mut Test| &mut test.a);
```
src/props.rs