If you are running the ArcGIS Python API in a virgin Conda environment, this very likely does not apply to you. If you are running the ArcGIS Python API in the Python environment installed with ArcGIS Pro, as of today 05Mar2018, you are stuck at version 1.2.5 while the current version is 1.4 - and includes a whole boatload of new functionality, particularly when it comes to the SpatialDataFrame.
This is due to the ArcGIS Python API shipping with ArcGIS Pro as of version 2.1. This is good, although it also means you now have to explicitly use the
--no-pin option to upgrade to the most current version. This actually is detailed in the documentation, although it did take me a while to find it. If you, like me, are impatient, open a Python command prompt as administrator, and use this command to upgrade.
conda upgrade -c esri --no-pin arcgis
Voila! Congratulations, you are upgraded.