either a character or an integer of which spread-sheet to read;
the number starts from 1
method
which method to use for reading the 'xlsx' file;
choices are 'auto' (automatically find proper method),
'pandas' (use pandas.read_xlsx), or 'readxl' (use the
corresponding R package)
n_max
maximum number of rows (excluding headers) to read
...
passed to 'Python' function pandas.read_xlsx or
readxl::read_excel, depending on method