Nested Dataframes causes exception

[pjmattingly]

import pystore
pystore.set_path("./pystore")
store = pystore.store('test')
collection = store.collection('demo collection')

df_path_and_hash = pd.DataFrame({'path': ['path1', 'path2'], 'hash': [0, 1]})
d_container = {'idx':[1], 'dfs':[df_path_and_hash]}
df_container = pd.DataFrame(d_container)

collection.write('test item', df_container)

item = collection.item('test item')

Which causes the exception:

Traceback (most recent call last):
  File "<user>\anaconda3\envs\dev1\lib\site-packages\fastparquet\api.py", line 110, in __init__
    with open_with(fn2, 'rb') as f:
  File "<user>\anaconda3\envs\dev1\lib\site-packages\fsspec\spec.py", line 940, in open
    f = self._open(
  File "<user>\anaconda3\envs\dev1\lib\site-packages\fsspec\implementations\local.py", line 118, in _open
    return LocalFileOpener(path, mode, fs=self, **kwargs)
  File "<user>\anaconda3\envs\dev1\lib\site-packages\fsspec\implementations\local.py", line 200, in __init__
    self._open()
  File "<user>\anaconda3\envs\dev1\lib\site-packages\fsspec\implementations\local.py", line 205, in _open
    self.f = open(self.path, mode=self.mode)
FileNotFoundError: [Errno 2] No such file or directory: '<user>/Documents/Professional Work/Work/dev, keyword check; a tool to help find text in files/pystore/test/demo collection/test item/part.0.parquet/_metadata'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "KC_dev.py", line 2329, in <module>
    main()
  File "KC_dev.py", line 54, in main
    item = collection.item('test item')
  File "<user>\anaconda3\envs\dev1\lib\site-packages\pystore\collection.py", line 78, in item
    return Item(item, self.datastore, self.collection,
  File "<user>\anaconda3\envs\dev1\lib\site-packages\pystore\item.py", line 60, in __init__
    self.data = dd.read_parquet(
  File "<user>\anaconda3\envs\dev1\lib\site-packages\dask\dataframe\io\parquet\core.py", line 307, in read_parquet
    read_metadata_result = engine.read_metadata(
  File "<user>\anaconda3\envs\dev1\lib\site-packages\dask\dataframe\io\parquet\fastparquet.py", line 678, in read_metadata
    parts, pf, gather_statistics, base_path = _determine_pf_parts(
  File "<user>\pmatt\anaconda3\envs\dev1\lib\site-packages\dask\dataframe\io\parquet\fastparquet.py", line 159, in _determine_pf_parts
    pf = ParquetFile(paths, open_with=fs.open, **kwargs.get("file", {}))
  File "<user>\anaconda3\envs\dev1\lib\site-packages\fastparquet\api.py", line 90, in __init__
    basepath, fmd = metadata_from_many(fn, verify_schema=verify,
  File "<user>\anaconda3\envs\dev1\lib\site-packages\fastparquet\util.py", line 134, in metadata_from_many
    pfs = [api.ParquetFile(fn, open_with=open_with) for fn in file_list]
  File "<user>\anaconda3\envs\dev1\lib\site-packages\fastparquet\util.py", line 134, in <listcomp>
    pfs = [api.ParquetFile(fn, open_with=open_with) for fn in file_list]
  File "<user>\anaconda3\envs\dev1\lib\site-packages\fastparquet\api.py", line 116, in __init__
    self._parse_header(f, verify)
  File "<user>\anaconda3\envs\dev1\lib\site-packages\fastparquet\api.py", line 133, in _parse_header
    f.seek(-(head_size+8), 2)
OSError: [Errno 22] Invalid argument

An un-nested dataframe causes no issue:

import pystore
pystore.set_path("./pystore")
store = pystore.store('test')
collection = store.collection('demo collection')

df_path_and_hash = pd.DataFrame({'path': ['path1', 'path2'], 'hash': [0, 1]})
d_container = {'idx':[1], 'dfs':[df_path_and_hash]}
df_container = pd.DataFrame(d_container)

collection.write('test item', df_path_and_hash)

item = collection.item('test item')