Goals:

• load DocumentArray from csv, with a given Document class to provide a schema
  • document_type needs to be set to determine schema.
  • column names have to match the Document types fields
  • for nested fields, use access paths as column name, such as 'image__url'
  • if value is None, leave csvfield empty, or enter None
• save a DocumentArray to csv
  • following the same guidelines as above.
• check and update documentation, if required. See guide