rest-assured/src/main/java/io/restassured/builder/MultiPartSpecBuilder.java
public MultiPartSpecBuilder charset(Charset charset) {
        Validate.notNull(charset, "Charset cannot be null");
        this.charset = charset.toString();
        return this;
    }
public MultiPartSpecBuilder charset(Charset charset) {
        Validate.notNull(charset, "Charset cannot be null");
        this.charset = charset.toString();
        return this;
    }
Specify the charset for this charset.

@param charset The charset to use
@return An instance of MultiPartSpecBuilder