get_storage: RuntimeDescriptor<[address: FixedSizeBinary<20>, key: FixedSizeBinary<32>], ResultPayload<Binary | undefined, Enum<{
    DoesntExist: undefined;
    KeyDecodingFailed: undefined;
}>>>

Query a given storage key in a given contract.

Returns Ok(Some(Vec<u8>)) if the storage value exists under the given key in the specified account and Ok(None) if it doesn't. If the account specified by the address doesn't exist, or doesn't have a contract then Err is returned.