code: def aggregation_request(
      self,
      client: "IClientAdapter",
      index: str,
      size: int = None,
  ) -> List[Dict[str, Any]]:
      schema = client.get_property_type(
          index=index,
          property_name="metadata",
      )
  
      metadata_aggs = aggregations.custom_fields(
          fields_definitions=schema,
          size=size,
      )
      return [{key: value} for key, value in metadata_aggs.items()]
  
imports: import dataclasses
  import logging
  from typing import TYPE_CHECKING, Any, Dict, List, Optional, Union
  from argilla.server.daos.backend.query_helpers import aggregations
  from argilla.server.helpers import unflatten_dict
label_desc: Use image node_id 2 for calling the MetadataAggregations obj's underlying member method code with example usage: obj.aggregation_request(client, index, size) and returns: unknown