multidict: remove to_dict

We never use it, and it is dangerously ambiguous when a key is associated with
a list.

mitmproxy/types/multidict.py

@@ -174,27 +174,6 @@ class _MultiDict(MutableMapping, serializable.Serializable, metaclass=ABCMeta):
                 coll.append([key, values])
         return coll
 
-    def to_dict(self):
-        """
-        Get the MultiDict as a plain Python dict.
-        Keys with multiple values are returned as lists.
-
-        Example:
-
-        .. code-block:: python
-
-            # Simple dict with duplicate values.
-            >>> d = MultiDict([("name", "value"), ("a", False), ("a", 42)])
-            >>> d.to_dict()
-            {
-                "name": "value",
-                "a": [False, 42]
-            }
-        """
-        return {
-            k: v for k, v in self.collect()
-        }
-
     def get_state(self):
         return self.fields
 

test/mitmproxy/test_types_multidict.py

@@ -172,13 +172,6 @@ class TestMultiDict:
         assert list(md.items()) == [("foo", "bar"), ("bar", "baz")]
         assert list(md.items(multi=True)) == [("foo", "bar"), ("bar", "baz"), ("Bar", "bam")]
 
-    def test_to_dict(self):
-        md = self._multi()
-        assert md.to_dict() == {
-            "foo": "bar",
-            "bar": ["baz", "bam"]
-        }
-
     def test_state(self):
         md = self._multi()
         assert len(md.get_state()) == 3