Optionally filter files by metadata. Uses Pinecone's metadata filter language:
fields are referenced at the top level (not wrapped in a metadata key), and
may be combined with operators like $eq, $ne, $gt, $lt, $in.
Filters that don't match Pinecone's expected shape (e.g. wrapping fields
in a top-level metadata key like { metadata: { version: 'v1' } }) are
silently ignored server-side and return the unfiltered file list.
Options for filtering files in the list operation.