Ran black and pylint fixes

Author: kmatch98

adafruit_display_shapes/sparkline.py

@@ -1,5 +1,8 @@
+# SPDX-FileCopyrightText: 2020 Kevin Matocha
+#
+# SPDX-License-Identifier: MIT
+
 # class of sparklines in CircuitPython
-# created by Kevin Matocha - Copyright 2020 (C)
 
 # See the bottom for a code example using the `sparkline` Class.
 
@@ -34,6 +37,8 @@
 
 """
 
+#pylint: disable=too-many-instance-attributes
+
 import displayio
 from adafruit_display_shapes.line import Line
 
@@ -85,6 +90,13 @@ def __init__(
             max_size=self._max_items - 1, x=x, y=y
         )  # self is a group of lines
 
+    def clear_values(self):
+        """Removes all values from the _spark_list list and removes all lines in the group"""
+
+        for _ in range(len(self)):  # remove all items from the current group
+            self.pop()
+        self._spark_list = []  # empty the list
+
     def add_value(self, value):
         """Add a value to the sparkline.
         :param value: The value to be added to the sparkline