new_contents: 
  '''exceptions used by the library'''
  
  
  class InvalidDelimiterError(Exception):
      '''Raised when invalid market-pair delimiter is used.'''
      pass
  
  
  class InvalidBaseCurrencyError(Exception):
      '''Raised when base currency you are trying to use is not support by the exchange,
         or when you are giving this method a wrong input.'''
      pass
  
subject: add exceptions file.