code: def start_vm(access_token, subscription_id, resource_group, vm_name):
      '''Start a virtual machine.
  
      Args:
          access_token (str): A valid Azure authentication token.
          subscription_id (str): Azure subscription id.
          resource_group (str): Azure resource group name.
          vm_name (str): Name of the virtual machine.
  
      Returns:
          HTTP response.
      '''
      endpoint = ''.join([get_rm_endpoint(),
                          '/subscriptions/', subscription_id,
                          '/resourceGroups/', resource_group,
                          '/providers/Microsoft.Compute/virtualMachines/',
                          vm_name,
                          '/start',
                          '?api-version=', COMP_API])
      return do_post(endpoint, '', access_tokenf start_vm(access_token, subscription_id, resource_group, vm_name):
      '''Start a virtual machine.
  
      Args:
          access_token (str): A valid Azure authentication token.
          subscription_id (str): Azure subscription id.
          resource_group (str): Azure resource group name.
          vm_name (str): Name of the virtual machine.
  
      Returns:
          HTTP response.
      '''
      endpoint = ''.join([get_rm_endpoint(),
                          '/subscriptions/', subscription_id,
                          '/resourceGroups/', resource_group,
                          '/providers/Microsoft.Compute/virtualMachines/',
                          vm_name,
                          '/start',
                          '?api-version=', COMP_API])
      return do_post(endpoint, '', access_token)
docs: Start a virtual machine.
  
      Args:
          access_token (str): A valid Azure authentication token.
          subscription_id (str): Azure subscription id.
          resource_group (str): Azure resource group name.
          vm_name (str): Name of the virtual machine.
  
      Returns:
          HTTP response.