Adapt the value if an adapter is defined.

def _adapt_param(self, key, val):
        """
        Adapt the value if an adapter is defined.
        """
        if key in self.param_adapters:
            try:
                return self.param_adapters[key](val)
            except (AdaptError, AdaptErrors, TypeError, ValueError) as e:
                if hasattr(e, 'errors'):
                    errors = e.errors
                else:
                    errors = [e]

                raise AnticipateParamError(
                    message='Input value %r for parameter `%s` does not match '
                        'anticipated type %r' % (type(val), key, self.params[key]),
                    name=key,
                    value=val,
                    anticipated=self.params[key],
                    errors=errors)
        else:
            return val