code: def camelcase_to_underscores(word):
      
      s1 = _FIRST_CAP_RE.sub(r'\1_\2', word)
      return _ALL_CAP_RE.sub(r'\1_\2', s1).lower()
docs: Converts a CamelCase word into an under_score word.
  
          >>> camelcase_to_underscores("CamelCaseCase")
          'camel_case_case'
          >>> camelcase_to_underscores("getHTTPResponseCode")
          'get_http_response_code'