title: How to set set JSON encoder in marshmallow?
body: <p>How do I override the JSON encoder used the <a href="https://github.com/marshmallow-code/marshmallow" rel="noreferrer">marshmallow</a> library so that it can serialize a <code>Decimal</code> field?I think I can do this by overriding <code>json_module</code> in the base <code>Schema</code> or <code>Meta</code> class, but I don't know how:</p>
  
  <p><a href="https://github.com/marshmallow-code/marshmallow/blob/dev/marshmallow/schema.py#L194" rel="noreferrer">https://github.com/marshmallow-code/marshmallow/blob/dev/marshmallow/schema.py#L194</a></p>
  
  <p>I trawled all the docs and read the code, but I'm not a Python native.</p>