Fixed FutureWarning re frame.append

Author: mbuchan-work

packages/python/plotly/plotly/express/_core.py

@@ -268,7 +268,7 @@ def make_trace_kwargs(args, trace_spec, trace_data, mapping_labels, sizeref):
         fit information to be used for trendlines
     """
     if "line_close" in args and args["line_close"]:
-        trace_data = trace_data.append(trace_data.iloc[0])
+        trace_data = trace_data.concat(trace_data.iloc[0], axis = 0, join = 'outer')
     trace_patch = trace_spec.trace_patch.copy() or {}
     fit_results = None
     hover_header = ""