The description of an argument of Quantopian's fetch_csv() function is the following:
A well-formed http or https url pointing to a CSV file that has a header, a date column, and a symbol column (symbol column required to match data to securities).
How can my CSV possibly have BOTH a date column and a symbol column? In my CSV, (created using pandas.DataFrame's to_csv() function), the dates occupy a column, but the symbols constitute a row, and it is blatantly obvious that if the dates are in a column, the symbols cannot also be. Can anyone explain this to me? Thank you.