class_docstr: Apply an offset and limit to the query based on the current page and number of
  items per page.
  
  Don't create pagination objects manually. They are created by
  :meth:`.SQLAlchemy.paginate` and :meth:`.Query.paginate`.
  
  This is a base class, a subclass must implement :meth:`_query_items` and
  :meth:`_query_count`. Those methods will use arguments passed as ``kwargs`` to
  perform the queries.
  
  :param page: The current page, used to calculate the offset. Defaults to the
      ``page`` query arg during a request, or 1 otherwise.
  :param per_page: The maximum number of items on a page, used to calculate the
      offset and limit. Defaults to the ``per_page`` query arg during a request,
      or 20 otherwise.
  :param max_per_page: The maximum allowed value for ``per_page``, to limit a
      user-provided value. Use ``None`` for no limit. Defaults to 100.
  :param error_out: Abort with a ``404 Not Found`` error if no items are returned
      and ``page`` is not 1, or if ``page`` or ``per_page`` is less than 1, or if
      either are not ints.
  :param count: Calculate the total number of values by issuing an extra count
      query. For very complex queries this may be inaccurate or slow, so it can be
      disabled and set manually if necessary.
  :param kwargs: Information about the query to paginate. Different subclasses will
      require different arguments.
  
  .. versionchanged:: 3.0
      Iterating over a pagination object iterates over its items.
  
  .. versionchanged:: 3.0
      Creating instances manually is not a public API.
docstr: The previous page number, or ``None`` if this is the first page.
docstr_tok: ["The","previous","page","number",",","or","``","None","``","if","this","is","the","first","page","."]
code: def prev_num(self) -> int | None:
      """The previous page number, or ``None`` if this is the first page."""
      if not self.has_prev:
          return None
  
      return self.page - 1
  
imports: from __future__ import annotations
  import typing
  from math import ceil
  import sqlalchemy
  import sqlalchemy.orm
  from flask import abort
  from flask import request
label_desc: Use image node_id 10 for calling the Pagination obj's underlying member method code with example usage: obj.prev_num() and returns: unknown, None