code: def calculate_uuid(self):
          
  
          # raise an error if no inputs to the UUID calculation were specified
          if self.uuid_input_fields is None:
              raise NotImplementedError("""You must define either a 'uuid_input_fields' attribute
                  (with a tuple of field names) or override the 'calculate_uuid' method, on models
                  that inherit from UUIDModelMixin. If you want a fully random UUID, you can set
                  'uuid_input_fields' to the string 'RANDOM'.""")
  
          # if the UUID has been set to be random, return a random UUID
          if self.uuid_input_fields == "RANDOM":
              return uuid.uuid4().hex
  
          # if we got this far, uuid_input_fields should be a tuple
          assert isinstance(self.uuid_input_fields, tuple), "'uuid_input_fields' must either be a tuple or the string 'RANDOM'"
  
          # calculate the input to the UUID function
          hashable_input_vals = []
          for field in self.uuid_input_fields:
              new_value = getattr(self, field)
              if new_value:
                  hashable_input_vals.append(str(new_value))
          hashable_input = ":".join(hashable_input_vals)
  
          # if all the values were falsey, just return a random UUID, to avoid collisions
          if not hashable_input:
              return uuid.uuid4().hex
  
          # compute the UUID as a function of the input values
          return sha2_uuid(hashable_input)
docs: Should return a 32-digit hex string for a UUID that is calculated as a function of a set of fields from the model.