bug: very slow export with model_attributes_to_shapefile about flopy

[spaulins-usgs]

@RyanConway91, so far I have not been able to reproduce this. I used "test050_create_tests_circle_island" from our tests in autotest\regression\test_mf6.py, and increased the number of layers to 400, so that the model has over 2,000,000 cells.

Exporting with "model_attributes_to_shapefile" took 35 seconds. Exporting with the code you provided above took 17 seconds. Note that "model_attributes_to_shapefile" exports more data than your code does, exported shapefiles are 119 MB vs 82 MB ("model_attributes_to_shapefile" also exports icelltype). In this case "model_attributes_to_shapefile" is running a little slower than your code (3.4 MB/sec vs 4.8 MB/sec), though nowhere near what you are describing.

Can you provide an example project to help me reproduce the problem?

[wpbonelli]

Feel free to reopen if needed @RyanConway91