docs: def main():
      '''Main routine.'''
      # check for single command argument
      if len(sys.argv) != 2:
          region = 'all'
      else:
          region = sys.argv[1]
  
      # Load Azure app defaults
      try:
          with open('azurermconfig.json') as config_file:
              config_data = json.load(config_file)
      except FileNotFoundError:
          sys.exit('Error: Expecting azurermconfig.json in current folder')
  
      tenant_id = config_data['tenantId']
      app_id = config_data['appId']
      app_secret = config_data['appSecret']
      sub_id = config_data['subscriptionId']
  
      access_token = azurerm.get_access_token(tenant_id, app_id, app_secret)
  
      # print quota
      if region == 'all':
          # list locations
          locations = azurerm.list_locations(access_token, sub_id)
          for location in locations['value']:
              print_region_quota(access_token, sub_id, location['name'])
      else:
          print_region_quota(access_token, sub_id, region)