json_normalize Support for Generators
The data argument in json_normalize requires be an dictionary or list of dictionaries. If an iterator is passed, unexpected behavior can occur. In particular, this will result in the loss of the first row. See https://stackoverflow.com/questions/56362810/missing-first-document-when-loading-multi-document-yaml-file-in-pandas-dataframe.

I think this should be catched, either by throwing an error (as proposed in https://github.com/pandas-dev/pandas/pull/26646) or by ensuring that the output for the iterator is the same as for the list created by "materializing" the iterator.
