approx_match
============
Return the items which match the most rules.

Function Arguments
------------------
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   :widths: 20 10 60
   :header-rows: 1
   :align: left

   * - Name
     - Type
     - Description

   * - rule
     - str, dict
     - The matched rule.

   * - max_mismatch
     - int
     - (optional; default: ``1``) The number of mismatched rules at most.

Description
-----------
This function is like :ref:`match function <MatchFunction>`, but it returns
the items that match the most rules when there's no items that match all
rules.

Examples
--------
There are 5 rules, 5 items and ``max_mismatch = 1`` in the following examples.

The number of matched rules are ``[0, 1, 2, 3, 4]``,
this function returns the last item that matches 4 rules.

The number of matched rules are ``[0, 1, 4, 4, 4]``,
this function returns the last 3 items that match 4 rules.

The number of matched rules are ``[0, 0, 0, 0, 0]``,
this function returns an empty list because there's no items that mismatch
less equal than 1 rule.

Result
------
The result is a list which contains the items that match the most rules.

For each result, the schema is like::

  {
    "perfect_match": a boolean indicating if the item matches all rules,
    "approx_match": {
      "matched_num": number of matched rules,
      "rule": {
        "rule_name": {
          "info": the rule string,
          "result": a boolean indicating if the item matches the rule
        },...
      }
    },
    "values": the probed results
  }