Adds group to docs

We hadn't exposed it. This adds that and corrects the doc string
that will be exposed.

docs/reference/api-reference/decorators.rst

@@ -53,6 +53,8 @@ Classes to help with @parameterize:
 
 .. autoclass:: hamilton.function_modifiers.value
 
+.. autoclass:: hamilton.function_modifiers.group
+
 
 Actual decorators:
 ^^^^^^^^^^^^^^^^^^^^^^^^^

hamilton/function_modifiers/dependencies.py

@@ -186,11 +186,13 @@ def group(
     This means that it gets injected into a list of dependencies that are grouped together. E.G.
     dep=group(source("foo"), source("bar")) for the function:
 
+    @inject(dep=group(source("foo"), source("bar")))
     def f(dep: List[pd.Series]) -> pd.Series:
         return ...
 
     Would result in dep getting foo and bar dependencies injected.
-    :param dependencies: Dependencies, list of dependencies
+    :param dependency_args: Dependencies, list of dependencies (e.g. source("foo"), source("bar"))
+    :param dependency_kwargs: Dependencies, kwarg dependencies (e.g. foo=source("foo"))
     :return:
     """
     _validate_group_params(dependency_args, dependency_kwargs)