@classmethod
def from_dict(cls, mapping):
    """Generate an iterable of Parameter from a dictionary.

        Args:
            mapping (mapping): Some mapping of query parameter fields to
                values. All values should be iterables of values even if there
                is only one.

        Returns:
            iter of Parameter: An iterable of parameters from the mapping.
        """
    for field, values in mapping.items():
        for value in values:
            yield cls(field, value)
