class_docstr: TGOS Geocoding Service
  
  TGOS Map is official map service of Taiwan.
  
  API Reference
  -------------
  http://api.tgos.nat.gov.tw/TGOS_MAP_API/Web/Default.aspx
code: def _get_api_key(cls, key=None):
      # Retrieves API Key from method argument first, then from Environment variables
      key = key or cls._KEY
  
      if not key:
          key = cls._get_tgos_key()
  
      # raise exception if not valid key found
      if not key and cls._KEY_MANDATORY:
          raise ValueError("Provide API Key")
  
      return key
  
imports: import re
  import requests
  import logging
  from geocoder.base import OneResult, MultipleResultsQuery
  from geocoder.keys import tgos_key
label_desc: Use image node_id 1 for calling the TgosQuery obj's underlying member method code with example usage: obj._get_api_key(cls, key) and returns: key