code: def file_name_error(file_name):
      
  
      if file_name == '' or file_name[0][0] == '-':
          raise IOError('Input file name not specified.')
  
      elif not os.path.isfile(file_name):
          raise IOError('Input file name [%s] not found!' % file_name)
docs: File name error
  
      This method checks if the input file name is valid.
  
      Parameters
      ----------
      file_name : str
          File name string
  
      Raises
      ------
      IOError
          If file name not specified or file not found