code: def get_only_element_from_collection(one_element_collection):
      
      if len(one_element_collection) != 1:
          raise AssertionError(u'Expected a collection with exactly one element, but got: {}'
                               .format(one_element_collection))
      return funcy.first(one_element_collection)
docs: Assert that the collection has exactly one element, then return that element.