code: def bq_cast(
      string_field: str, bq_type: str
  ) -> None | int | float | bool | str:
      """
      Helper method that casts a BigQuery row to the appropriate data types.
  
      This is useful because BigQuery returns all fields as strings.
      """
      if string_field is None:
          return None
      elif bq_type == "INTEGER":
          return int(string_field)
      elif bq_type in ("FLOAT", "TIMESTAMP"):
          return float(string_field)
      elif bq_type == "BOOLEAN":
          if string_field not in ["true", "false"]:
              raise ValueError(
                  f"{string_field} must have value 'true' or 'false'"
              )
          return string_field == "true"
      else:
          return string_field
  
imports: from __future__ import annotations
  from typing import Any
label_desc: Use image node_id 1 for calling a global function with example usage: bq_cast(string_field, bq_type) and returns: None, int, float, unknown, string_field