'Convenience method that provides a quick way to add an email group
grant to a key. This method retrieves the current ACL, creates a new
grant based on the parameters passed in, adds that grant to the ACL and
then PUT\'s the new ACL back to GS.
:type permission: string
:param permission: The permission being granted. Should be one of:
READ|FULL_CONTROL
See http://code.google.com/apis/storage/docs/developer-guide.html#authorization
for more details on permissions.
:type email_address: string
:param email_address: The email address associated with the Google
Group to which you are granting the permission.'

def add_group_email_grant(self, permission, email_address, headers=None):

    acl = self.get_acl(headers=headers)
    acl.add_group_email_grant(permission, email_address)
    self.set_acl(acl, headers=headers)
