I am having issues with getting a function field to display a string returned by a function in a custom module I am using to extend the stock.picking.out form. Ideally I would like to have a specific string from a field stored in the database displayed but that's an issue for another time because I can't even get a generic string to display..

Here is my field definition within my custom class:

```
_columns = {
    'my_field_name': fields.function(_my_func, type='char', string='description', store=True, method=True, readonly=True),
}

```

Here is my definition for '\_my\_func':

```
def _my_func(self, cr, uid, ids, field_name, arg, context=None):
    str="some string to be displayed"
    return str

```

Here is the XML for the field:

```
<field name="my_field_name" string="Here is my string:" class="oe_inline"/>

```

I have searched the OpenERP dev book as well as their forums and these forums, and believe I have followed all of the proper syntax for this field so any help is greatly appreciated.