The load_data function can be called with just a filename and path argument, in which case all the default arguments will be used. In this case, two columns from the text file will be read into a Data1D data set as "x" and "y". The user can specify which columns to read from the file by their column names in the order as they correspond to the data arrays in the data set. If no columns names are present, defaults will be assigned. (e.g., "col1", "col2", ...) The default data set, Data1D, uses the order: x, y, staterror, syserror for data arrays. Data set IDs can be integers or strings; in the latter case a string can denote useful information about the data (e.g., whether it is your source or background data set).