'Remove item from dictionary.
Args:
key: Key of item to remove.  Key is case insensitive, so "del d[\'Key\']" is
the same as "del d[\'key\']"'

def __delitem__(self, key):

    caseless_key = key.lower()
    del self.data[self.caseless_keys[caseless_key]]
    del self.caseless_keys[caseless_key]
