docs: 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