BUG: Fix deprecation warning on using PdfMerger

PyPDF2/merger.py

@@ -29,7 +29,7 @@
 from sys import version_info
 
 from PyPDF2._reader import PdfReader
-from PyPDF2._utils import DEPR_MSG, isString, str_
+from PyPDF2._utils import _isString, DEPR_MSG, str_
 from PyPDF2._writer import PdfWriter
 from PyPDF2.constants import PagesAttributes as PA
 from PyPDF2.generic import *
@@ -130,7 +130,7 @@ def merge(
  # BytesIO (or StreamIO) stream.
  # If fileobj is none of the above types, it is not modified
  decryption_key = None
- if isString(fileobj):
+ if _isString(fileobj):
  fileobj = file(fileobj, "rb")
  my_file = True
  elif hasattr(fileobj, "seek") and hasattr(fileobj, "read"):
@@ -185,7 +185,7 @@ def merge(
  else:
  self.bookmarks += outline
 
- dests = reader.namedDestinations
+ dests = reader.named_destinations
  trimmed_dests = self._trim_dests(reader, dests, pages)
  self.named_dests += trimmed_dests
 
@@ -241,7 +241,7 @@ def write(self, fileobj):
  file-like object.
  """
  my_file = False
- if isString(fileobj):
+ if _isString(fileobj):
  fileobj = file(fileobj, "wb")
  my_file = True