def subnets_list(resource_group_name, vnet_name, address_prefix = nil)
      list = network_resource_client.subnets.list(resource_group_name, vnet_name)
      !address_prefix.nil? && !list.empty? ? subnets_list_for_specific_address_space(address_prefix, list) : list
    end
def subnets_list(resource_group_name, vnet_name, address_prefix = nil)
      list = network_resource_client.subnets.list(resource_group_name, vnet_name)
      !address_prefix.nil? && !list.empty? ? subnets_list_for_specific_address_space(address_prefix, list) : list
    end
lists all subnets under a virtual network or lists subnets of only a particular address space