Unable to parse parquet files with maps with complex keys

**Describe the bug**
There's currently an assertion that forbids complex key types in parquet maps. No such restriction exists in the spec for parquet.

**To Reproduce**
Try to parse a parquet file with a map with an array key

**Expected behavior**
It should parse fine

Start by locating the assertion that forbids complex key types in parquet maps, then reproduce the issue with a parquet file whose map key is an array. The work is done when that file parses successfully without violating the parquet specification.

Written by the indexing model from the issue text.