code: def where_entry_category(query, category, recurse=False):
      
  
      category = str(category)
      if category and recurse:
          # We're recursing and aren't in /, so add the prefix clause
          return orm.select(
              e for e in query
              if e.category == category or e.category.startswith(category + '/')
          )
  
      if not recurse:
          # We're not recursing, so we need an exact match on a possibly-empty
          # category
          return orm.select(e for e in query if e.category == category)
  
      # We're recursing and have no category, which means we're doing nothing
      return query
docs: Generate a where clause for a particular category