GraphQL Mutation how to make fields optional to update fields only by selection and generate schema

I have a graphql mutation defined as follows

```
updateParts(
partId: String!
parts: PartRequest!
): UpdatePartsResponse!

input PartRequest {
name: String!
image: Strings!
boltTypes: [Bolts]!
}

input Bolts {
code: String!
metadata: String!
}

```

and the requirement was to update fields upon selection like

* update all

```
mutation {
updateParts(
partId: "0x1223"
parts: {
name: "some"
image: "dark.png"
boltTypes: [
{ code: "A", metadata: "B" }

]
}
)
}
}
```

* Update by selection name only
```
mutation {
updateParts(
partId: "0x1223"
parts: {
name: "some"

}
)
}
}
```

Update by selection , parts only

```
mutation {
updateParts(
partId: "0x1223"
parts: {

boltTypes: [
{ code: "A", metadata: "B" }

]
}
)
}
}
```

How to construct a schema to achieve this ?