When using FeatureLayer from arcgis.features, querying with a complex geometry triggers a JSONDecodeError. The problem appears to be that queries are running as GET ...
"For ArcGIS 10.2 and 10.3"--Front cover. Preface -- Acknowledgments -- Part 1: Getting To Know GIS: -- Introducing GIS -- Introducing ArcGIS -- Part 2: Getting Started With Maps And Data: -- ...
https://services.arcgis.com/P3ePLMYs2RVChkJx/arcgis/rest/services/Resolve_Ecoregions/FeatureServer/query?layerDefs=%5B%7B+%22layerId%22+%3A+%220%22%2C%22where%22%3A ...