    # File lib/active_merchant/billing/gateways/paypal/paypal_common_api.rb, line 63
          def initialize(options = {})
            requires!(options, :login, :password)

            @options = {
              :pem => pem_file,
              :signature => signature
            }.update(options)

            if @options[:pem].blank? && @options[:signature].blank?
              raise ArgumentError, "An API Certificate or API Signature is required to make requests to PayPal"
            end

            super
          end