This is a pre-release version of Kaleido 1.0.0 which contains a number of breaking changes relative to Kaleido 0.x. It is not compatible with the latest release of Plotly. To generate images with Plotly you should install the latest stable version of and Kaleido (v0.2.1).
Documentation for the new API can be found in the README: https://github.com/plotly/Kaleido