OHLCHelper.validate_data

You're seeing just the function validate_data, go back to OHLCHelper module for more information.
Link to this function

validate_data(candles \\ [], trades \\ [])

Specs

validate_data(OHLC.candles() | nil, OHLC.trades() | nil) ::
  :ok | {:error, atom()}

Validates the data used for generating the OHLC candles. Accepts lists of candles, trades or both.