<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def ifo(self):
 """Return the ifo. If only one ifo in the ifo list this will be that ifo. Otherwise an error is raised. """

        if self.ifo_list and len(self.ifo_list) == 1:
            return self.ifo_list[0]
        else:
            errMsg = "self.ifoList must contain only one ifo to access the "
            errMsg += "ifo property. %s." %(str(self.ifo_list),)
            raise TypeError(errMsg)