I am new to azure.I am learning azure python sdk and have some doubts.

1. I am not using any credentials to log in azure account and still can access 
VM's in subscription in my code below, how?
2. I am trying to get list of all VM's using `list_all()` which is present in azure doc <https://learn.microsoft.com/en-us/python/api/azure-mgmt-compute/azure.mgmt.compute.v2018_10_01.operations.virtualmachinesoperations?view=azure-python#list-all-custom-headers-none--raw-false----operation-config->
, How can i get list of VM's or how to iterate over `VirtualMachinePaged object` return by `list_all()` to get list of VM's?
3. When i tried to print name of VM using `#print(client.virtual_machines.get(resource_group_name='GSLab', vm_name='GSLabVM2'))` i got error `Resource group 'GSLab' could not be found.`, i checked and sure that name of resource group in 'GSLab', so why am i getting this error?

Here is my code, Thank you and please suggest any other source for better understanding of these concepts if possible.

```
from azure.common.client_factory import get_client_from_auth_file
from azure.mgmt.compute import ComputeManagementClient

client = get_client_from_auth_file(ComputeManagementClient)
#print(client)

vmlist = client.virtual_machines.list_all()
print(vmlist)
for vm in vmlist:
    print(vm.name)

print(client.virtual_machines.get(resource_group_name='GSLab', vm_name='GSLabVM2'))

```