Function mpl_token_metadata::processor::try_get_account_info

pub fn try_get_account_info<'a>(
    accounts: &'a [AccountInfo<'a>],
    index: usize
) -> Result<&'a AccountInfo<'a>, ProgramError>

Convenience function for accessing an AccountInfo by index and validating whether the account is present or not.

This relies on the client setting the crate::id() as the pubkey for accounts that are not set, which effectively allows us to use positional optional accounts.