code: def to_lower(self, string):
          "Helper function to transform strings to lower case"
          value = None
          try:
              value = string.lower()
          except AttributeError:
              value = ""
          finally:
              return valuf to_lower(self, string):
          "Helper function to transform strings to lower case"
          value = None
          try:
              value = string.lower()
          except AttributeError:
              value = ""
          finally:
              return value
docs: Helper function to transform strings to lower case