# File lib/aws/core/signature/version_4.rb, line 40
        def authorization credentials, datetime
          parts = []
          parts << "AWS4-HMAC-SHA256 Credential=#{credentials.access_key_id}/#{credential_string(datetime)}"
          parts << "SignedHeaders=#{signed_headers}"
          parts << "Signature=#{signature(credentials, datetime)}"
          parts.join(', ')
        end