Cannot use for k, v in X with "hashmap"-like data structures

[alpharder]

Description

Error: cannot unpack: not a sequence while trying to iterate over with JSON-object hash-map alike values.

Reproduction steps

1. At playground (WASM):

2. I initially reproduced this locally when passing `serde_json::Value` based as template rendering context:

Additional helpful information:

• Version of minijinja: 0.30.7
• Version of rustc: rustc 1.67.1 (d5a82bbd2 2023-02-07)
• Operating system and version: MacOS

What did you expect

I expect this to iterate over key-value pairs

[mitsuhiko]

To iterate over key value pairs you need to use |items or |dictsort:

{% for key, value in my_dict|items %}
  {{ key }}: {{ value }}
{% endfor %}

Or alternatively

{% for key in my_dict %}
  {{ key }}: {{ my_dict[key] }}
{% endfor %}