STY: Modify error messages.

Also some documentation tweaks in PdfWriter

tests/test_writer.py

@@ -1187,21 +1187,21 @@ def test_set_page_label(pdf_file_path):
  writer = PdfWriter()
  writer.clone_document_from_reader(reader)
  with pytest.raises(
- ValueError, match="at least one between style and prefix must be given"
+ ValueError, match="at least one of style and prefix must be given"
  ):
  writer.set_page_label(0, 5, start=2)
  with pytest.raises(
- ValueError, match="page_index_from must be equal or greater then 0"
+ ValueError, match="page_index_from must be greater or equal than 0"
  ):
  writer.set_page_label(-1, 5, "/r")
  with pytest.raises(
- ValueError, match="page_index_to must be equal or greater then page_index_from"
+ ValueError, match="page_index_to must be greater or equal than page_index_from"
  ):
  writer.set_page_label(5, 0, "/r")
  with pytest.raises(ValueError, match="page_index_to exceeds number of pages"):
  writer.set_page_label(0, 19, "/r")
  with pytest.raises(
- ValueError, match="if given, start must be equal or greater than one"
+ ValueError, match="if given, start must be greater or equal than one"
  ):
  writer.set_page_label(0, 5, "/r", start=-1)