constructor (call, type) {
    this.call = call
    this.type = type
    if (call.metadata instanceof grpc.Metadata) {
      this.metadata = call.metadata.getMap()
    } else {
      this.metadata = call.metadata
    }

    if (type === CallType.RESPONSE_STREAM ||
      type === CallType.UNARY) {
      this.req = call.request
    } else {
      this.req = call
    }
  }
Creates a Mali Request instance
@param {Object} call the grpc call instance
@param {String} type the call type. one of `@malijs/call-types` enums.