@classmethod
def from_dicts(cls, ctx, overrides=None, defaults=None):
    """Creates a context introducing both defaults and overrides.

        This combines both the standard constructor and `from_defaults`:meth:.

        If the same key appears in both `overrides` and `defaults`, ignore the
        default.

        """
    if not overrides:
        overrides = {}
    if not defaults:
        defaults = {}
    current = cls[ctx]
    current_attrs = dict(current) if current else {}
    attrs = dict(defaults, **current_attrs)
    attrs.update(overrides)
    return cls(ctx, **attrs)
