'Appends a blank page to this PDF file and returns it. If no page size
is specified, use the size of the last page.
:param float width: The width of the new page expressed in default user
space units.
:param float height: The height of the new page expressed in default
user space units.
:return: the newly appended page
:rtype: :class:`PageObject<PyPDF2.pdf.PageObject>`
:raises PageSizeNotDefinedError: if width and height are not defined
and previous page does not exist.'

def addBlankPage(self, width=None, height=None):

    page = PageObject.createBlankPage(self, width, height)
    self.addPage(page)
    return page
