fix python 3.5/6 warnings: [...]/elasticsearch/client/__init__.py:884: DeprecationWarning: invalid escape sequence \_ (elastic#665)

https://bugs.python.org/issue27364

Author: d9pouces

elasticsearch/client/__init__.py

@@ -574,7 +574,7 @@ def search(self, index=None, doc_type=None, body=None, params=None):
             choices are: 'open', 'closed', 'none', 'all'
         :arg explain: Specify whether to return detailed information about score
             computation as part of a hit
-        :arg from\_: Starting offset (default: 0)
+        :arg from\\_: Starting offset (default: 0)
         :arg ignore_unavailable: Whether specified concrete indices should be
             ignored when unavailable (missing or closed)
         :arg lenient: Specify whether format-based query failures (such as
@@ -674,7 +674,7 @@ def update_by_query(self, index, doc_type=None, body=None, params=None):
         :arg expand_wildcards: Whether to expand wildcard expression to concrete
             indices that are open, closed or both., default 'open', valid
             choices are: 'open', 'closed', 'none', 'all'
-        :arg from\_: Starting offset (default: 0)
+        :arg from\\_: Starting offset (default: 0)
         :arg ignore_unavailable: Whether specified concrete indices should be
             ignored when unavailable (missing or closed)
         :arg lenient: Specify whether format-based query failures (such as
@@ -810,7 +810,7 @@ def delete_by_query(self, index, body, doc_type=None, params=None):
         :arg expand_wildcards: Whether to expand wildcard expression to concrete
             indices that are open, closed or both., default 'open', valid
             choices are: 'open', 'closed', 'none', 'all'
-        :arg from\_: Starting offset (default: 0)
+        :arg from\\_: Starting offset (default: 0)
         :arg ignore_unavailable: Whether specified concrete indices should be
             ignored when unavailable (missing or closed)
         :arg lenient: Specify whether format-based query failures (such as