code: def _validate_file_formats(input_filepath_list, combine_type):
      '''Validate that combine method can be performed with given files.
      Raises IOError if input file formats are incompatible.
      '''
      _validate_sample_rates(input_filepath_list, combine_type)
  
      if combine_type == 'concatenate':
          _validate_num_channels(input_filepath_list, combine_typef _validate_file_formats(input_filepath_list, combine_type):
      '''Validate that combine method can be performed with given files.
      Raises IOError if input file formats are incompatible.
      '''
      _validate_sample_rates(input_filepath_list, combine_type)
  
      if combine_type == 'concatenate':
          _validate_num_channels(input_filepath_list, combine_type)
docs: Validate that combine method can be performed with given files.
      Raises IOError if input file formats are incompatible.