Unexpected Name "mutations"

hi:
i use relay mutation in order to create ,but struggle an problem

this is my mutation：
```
`
const mutation = graphql`
mutation createCourseMutation(
$input: CreateCourseMutationInput!
) {
createCourse(input : $input) {
course {
id
name
desc
detail
image
degree
category
}
}
}
`;
```
`
but the data which is received by server from client is as follows:

```
**mutations** createCourseMutation(
$input: CreateCourseMutationInput!
) {
createCourse(input: $input) {
course {
id
name
desc
detail
image
degree
category
}
}
}
```

so the error is:
`Syntax Error GraphQL request (1:1) Unexpected Name "mutations"`

I don't understand why the mutation in graphql tag become mutations,

thanks