COMPAT: explictly cast numpy floats to native floats (#163)

* COMPAT: explictly cast numpy floats to native floats

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: martinfleis

branca/colormap.py

@@ -95,9 +95,13 @@ def __init__(self, vmin=0.0, vmax=1.0, caption="", max_labels=10):
     def render(self, **kwargs):
         """Renders the HTML representation of the element."""
         self.color_domain = [
-            self.vmin + (self.vmax - self.vmin) * k / 499.0 for k in range(500)
+            float(self.vmin + (self.vmax - self.vmin) * k / 499.0) for k in range(500)
         ]
         self.color_range = [self.__call__(x) for x in self.color_domain]
+
+        # sanitize possible numpy floats to native python floats
+        self.index = [float(i) for i in self.index]
+
         if self.tick_labels is None:
             self.tick_labels = legend_scaler(self.index, self.max_labels)