def coerce_default(self, value, resource):
return str(value)<EOL>
Coerce a value using a default converter, ``str()``.

        Arguments
        ---------
        value : ?
            The value to be coerced.
        resource : dataql.resources.Resource
            The ``Resource`` object used to obtain this value from the original one.

        Returns
        -------
        str
            The coerced value.

        Example
        -------

        >>> from dataql.solvers.registry import Registry
        >>> registry = Registry()
        >>> from datetime import date
        >>> registry.register(date)
        >>> solver = AttributeSolver(registry)
        >>> solver.coerce_default(date(2015, 6, 1), None)
        '2015-06-01'
        >>> solver.coerce_default(date, None)
        "<class 'datetime.date'>"