Update delete_series docstring to differentiate between drop_database (influxdata#699)

Closes influxdata#666

Signed-off-by: Matthew McGinn <[email protected]>

Author: xginn8

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Changed
 - Update test suite to add support for Python 3.7 and InfluxDB v1.6.4 and 1.7.4 (#692 thx @clslgrnc)
 - Update classifiers tuple to list in setup.py (#697 thx @Hanaasagi)
+- Update documentation for empty `delete_series` confusion
 
 ### Removed
 

influxdb/client.py

@@ -841,7 +841,9 @@ def set_user_password(self, username, password):
     def delete_series(self, database=None, measurement=None, tags=None):
         """Delete series from a database.
 
-        Series can be filtered by measurement and tags.
+        Series must be filtered by either measurement and tags.
+        This method cannot be used to delete all series, use
+        `drop_database` instead.
 
         :param database: the database from which the series should be
             deleted, defaults to client's current database