Ultimately, I need to generate a AccessKeyId, SecirutyKey and SessionToken for a user in a Cognito User Pool so I can test a lambda function as a cognito user using Postman. So far, I've spent 2 days trying to figure this out. It seems that this would work:

```
aws sts assume-role-with-web-identity --role-arn arn:aws:iam::1234567890:role/rolename--role-session-name "RoleSession1" --web-identity-token ??? --provider-id provideridvalue

```

I was able to get the provider-id value but I'm having trouble getting a valid value for the web-identity-token. 

If I understand correctly this should get me the web-identity-token:

```
aws cognito-idp initiate-auth --auth-flow USER_PASSWORD_AUTH --client-id clientidvalue --auth-parameters USERNAME=usernamevalue,PASSWORD=passwordvalue

```

I obtained the clientidvalue from the Federated Identities pool.

The problem I have been unable to resolve is that the above command gives me this error:

> 
> Unknown options: PASSWORD=<password>
> 
> 
> 

I've tried many different variations including json format but nothing works. What am I doing wrong?