githubv4.go
func (c *Client) Mutate(ctx context.Context, m interface{}, input Input, variables map[string]interface{}) error {
	if variables == nil {
		variables = map[string]interface{}{"input": input}
	} else {
		variables["input"] = input
	}
	return c.client.Mutate(ctx, m, variables)
}
func (c *Client) Mutate(ctx context.Context, m interface{}, input Input, variables map[string]interface{}) error {
	if variables == nil {
		variables = map[string]interface{}{"input": input}
	} else {
		variables["input"] = input
	}
	return c.client.Mutate(ctx, m, variables)
}
// Mutate executes a single GraphQL mutation request,
// with a mutation derived from m, populating the response into it.
// m should be a pointer to struct that corresponds to the GitHub GraphQL schema.
// Provided input will be set as a variable named "input".