yaml file multiple groups throws openstack.exceptions.ConfigException Cloud not found

[Saeed Fazlollahzadeh]

Today I faced an error but I'm not sure what to add in the original module's codes to fix.

This is my yaml file:
```
clouds:

  all:
    region1:
      auth:
        auth_url: http://openstack.me.com:5000
        application_credential_id: "test_creds"
        application_credential_secret: "test_cred_secret"
      regions:
      - RegionOne
      interface: "public"
      identity_api_version: 3
      auth_type: "v3applicationcredential"
    region2:
      auth:
        auth_url: http://openstack.me.com:5000
        application_credential_id: "test_creds"
        application_credential_secret: "test_cred_secret"
      regions:
      - RegionTwo
      interface: "public"
      identity_api_version: 3
      auth_type: "v3applicationcredential"
    region3:
      auth:
        auth_url: http://openstack.me.com:5000
        application_credential_id: "test_creds"
        application_credential_secret: "test_cred_secret"
      regions:
      - RegionThree
      interface: "public"
      identity_api_version: 3
      auth_type: "v3applicationcredential"

  regionA:
    region1:
      auth:
        auth_url: http://openstack.me.com:5000
        application_credential_id: "test_creds"
        application_credential_secret: "test_cred_secret"
      regions:
      - RegionOne
      interface: "public"
      identity_api_version: 3
      auth_type: "v3applicationcredential"

  regionB:
    region2:
      auth:
        auth_url: http://openstack.me.com:5000
        application_credential_id: "test_creds"
        application_credential_secret: "test_cred_secret"
      regions:
      - RegionTwo
      interface: "public"
      identity_api_version: 3
      auth_type: "v3applicationcredential"
    region3:
      auth:
        auth_url: http://openstack.me.com:5000
        application_credential_id: "test_creds"
        application_credential_secret: "test_cred_secret"
      regions:
      - RegionThree
      interface: "public"
      identity_api_version: 3
      auth_type: "v3applicationcredential"
```
This is my python code that I'm trying to iterate over `regionB`'s regions to check the server list:
```
import openstack
import yaml

with open('clouds.yaml', 'r') as f:
    reg = yaml.safe_load(f)

all_regions = []
for name in reg['clouds']['all']:
    all_regions.append(name)

regionA = []
for name in reg['clouds']['regionA']:
    iran_regions.append(name)

regionB = []
for name in reg['clouds']['regionB']:
    foreign_regions.append(name)

# Initialize and turn on debug logging
openstack.enable_logging(debug=False)

# Initialize connection
for region in all_regions:
    conn1 = openstack.connect(cloud=region) # tried this
    # conn2 = openstack.connect(cloud=f"['regionB']['{region}']") # and also tried this
    # List the servers
    for server in conn1.compute.servers():
    # for server in conn2.compute.servers():
        if server['name'] == 'some-name':
            result = server.to_dict()
            result
```
This is the error I get for `conn1`:
```
openstack.exceptions.ConfigException: Cloud region1 was not found.
```
And this is the error of `conn2`:
```
openstack.exceptions.ConfigException: Cloud ["regionB"]["region1"] was not found.
```
I checked [loader.py](https://github.com/openstack/openstacksdk/blob/master/openstack/config/loader.py) file and it seems it only checks if the order is like this in the `clouds.yaml`:
```
clouds:
 region1:
 region2:
 region3:
```
But I'm going to have some groups in a single file. I know I can have multiple file but I'm looking for a way to see if I can do what I'm looking for.

At this moment I'm not sure how to edit the files to achieve what I want, but if I found I'll update this PR.