code: def check_token_type(token_type):
      
      return check_string(token_type, min_length=1, max_length=LENGTHS['namespace_id'], pattern='^{}$|{}'.format(TOKEN_TYPE_STACKS, OP_NAMESPACE_PATTERN))
docs: Verify that a token type is well-formed
  
      >>> check_token_type('STACKS')
      True
      >>> check_token_type('BTC')
      False
      >>> check_token_type('abcdabcdabcd')
      True
      >>> check_token_type('abcdabcdabcdabcdabcd')
      False