docs: def get_proficiency_lookup_session(self):
          """Gets the OsidSession associated with the proficiency lookup
          service.
  
          return: (osid.learning.ProficiencyLookupSession) - a
                  ProficiencyLookupSession
          raise:  OperationFailed - unable to complete request
          raise:  Unimplemented - supports_proficiency_lookup() is false
          compliance: optional - This method must be implemented if
                      supports_proficiency_lookup() is true.
  
          """
          if not self.supports_proficiency_lookup():
              raise Unimplemented()
          try:
              from . import sessions
          except ImportError:
              raise OperationFailed()
          try:
              session = sessions.ProficiencyLookupSession(runtime=self._runtime)
          except AttributeError:
              raise OperationFailed()
          return session