code: def read_file(fname, *args, **kwargs):
      
      if not isstr(fname):
          raise ValueError('reading multiple files not supported, '
                           'please use `pyam.IamDataFrame.append()`')
      logger().info('Reading `{}`'.format(fname))
      format_kwargs = {}
      # extract kwargs that are intended for `format_data`
      for c in [i for i in IAMC_IDX + ['year', 'time', 'value'] if i in kwargs]:
          format_kwargs[c] = kwargs.pop(c)
      return format_data(read_pandas(fname, *args, **kwargs), **format_kwargs)
docs: Read data from a file saved in the standard IAMC format
      or a table with year/value columns