update

README.md

@@ -9,7 +9,6 @@ You can derive the `Model` and `Referencable` traits for your struct. This will
 
 ```rust
 use serde::{Deserialize, Serialize};
-use mongod::Historic;
 use mongod::Validate;
 use mongod::Reference;
 use mongod::derive::{Module, Referencable};
@@ -22,8 +21,8 @@ struct MyStruct {
 }
 
 impl Validate for MyStruct {
-    async fn validate(&self) -> bool {
-        true
+    async fn validate(&self) -> Result<(), String> {
+        Ok(())
     }
 }
 ```
@@ -86,12 +85,12 @@ struct YetAnotherStruct {
 }
 
 impl Validate for MyStruct {
-    async fn validate(&self) -> bool {
+    async fn validate(&self) -> Result<(), String> {
         if let Some(other) = self.other {
             assert_reference_of!(other, OtherStruct, YetAnotherStruct);
         }
 
-        true
+        Ok(())
     }
 }
 ```