Rack import error

After I set up maas according to the documentation, I encountered this problem:
“Rack import error - Unable to find a copy of bootx64.efi, grubx64.efi in the SimpleStream and the packages shim-signed, and grub-efi-amd64-signed are not installed. The uefi_ebc_tftp bootloader type may not work.”
this is the picture

how should i solve it?