def migrate_process_schema(self, process, schema, from_state):
        """Migrate process schema.

        :param process: Process instance
        :param schema: Process schema to migrate
        :param from_state: Database model state
        :return: True if the process was migrated, False otherwise
        """
        container = dict_dot(schema, '.'.join(self.field[:-1]), default=list)

        # Ignore processes, which already contain the target field.
        migrate = False
        for field in container:
            if field['name'] == self.field[-1]:
                field['name'] = self.new_field
                migrate = True
                break
            elif field['name'] == self.new_field:
                # Already has target field.
                migrate = False
                break
        else:
            if not self.skip_no_field:
                raise ValueError(
                    "Unable to rename: there is no field with name '{field}' or '{new_field}'.".format(
                        field=self.field[-1],
                        new_field=self.new_field,
                    )
                )

        return migrate