[tune] Reduce sampling API clutter (#4739)

Adds some sugar for tune sampling API (for commonplace sampling idioms).

python/ray/tune/suggest/__init__.py

@@ -1,16 +1,11 @@
 from ray.tune.suggest.search import SearchAlgorithm
 from ray.tune.suggest.basic_variant import BasicVariantGenerator
 from ray.tune.suggest.suggestion import SuggestionAlgorithm
-from ray.tune.suggest.variant_generator import grid_search, function, \
-    sample_from
+from ray.tune.suggest.variant_generator import grid_search
 
 __all__ = [
-    "SearchAlgorithm",
-    "BasicVariantGenerator",
-    "SuggestionAlgorithm",
-    "grid_search",
-    "function",
-    "sample_from",
+    "SearchAlgorithm", "BasicVariantGenerator", "SuggestionAlgorithm",
+    "grid_search"
 ]
 
 

python/ray/tune/suggest/variant_generator.py

@@ -9,6 +9,7 @@ import random
 import types
 
 from ray.tune import TuneError
+from ray.tune.sample import sample_from
 
 logger = logging.getLogger(__name__)
 
@@ -54,49 +55,6 @@ def grid_search(values):
     return {"grid_search": values}
 
 
-class sample_from(object):
-    """Specify that tune should sample configuration values from this function.
-
-    The use of function arguments in tune configs must be disambiguated by
-    either wrapped the function in tune.sample_from() or tune.function().
-
-    Arguments:
-        func: An callable function to draw a sample from.
-    """
-
-    def __init__(self, func):
-        self.func = func
-
-    def __str__(self):
-        return "tune.sample_from({})".format(str(self.func))
-
-    def __repr__(self):
-        return "tune.sample_from({})".format(repr(self.func))
-
-
-class function(object):
-    """Wraps `func` to make sure it is not expanded during resolution.
-
-    The use of function arguments in tune configs must be disambiguated by
-    either wrapped the function in tune.sample_from() or tune.function().
-
-    Arguments:
-        func: A function literal.
-    """
-
-    def __init__(self, func):
-        self.func = func
-
-    def __call__(self, *args, **kwargs):
-        return self.func(*args, **kwargs)
-
-    def __str__(self):
-        return "tune.function({})".format(str(self.func))
-
-    def __repr__(self):
-        return "tune.function({})".format(repr(self.func))
-
-
 _STANDARD_IMPORTS = {
     "random": random,
     "np": numpy,