text: Title: ATRTS not included in df.ta.study("volatility")
  Body: Using the latest version of develop, `Average True Range Trailing Stop: atrts`, isn't included in `df.ta.study("volatility")`. To be honest, I'm not entirely sure why. Things appears to be set up right.
  
  ```python
  Python 3.8.13 (default, Mar 18 2022, 02:13:38) 
  [GCC 11.2.0] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  >>> import pandas_ta as ta
  >>> print(ta.version)
  0.3.59b0
  >>> import talib
  >>> import pytz
  >>> from datetime import datetime
  >>> from config import OUTPUT_DIR
  >>> import numpy as np
  >>> timezone = pytz.utc
  >>> date_range = ["20200801", "20200901"]
  >>> start_date = timezone.localize(datetime.strptime(date_range[0], "%Y%m%d"))
  >>> end_date = timezone.localize(datetime.strptime(date_range[1], "%Y%m%d"))
  >>> data = pd.read_feather(f"{OUTPUT_DIR}/BTC.feather")
  >>> df = data[data["Datetime"].between(left=start_date, right=end_date, inclusive="both")]
  >>> df.set_index(pd.DatetimeIndex(df["Datetime"]), inplace=True)
  >>> df.ta.study("volatility")
  >>> df.columns
  Index(['Datetime', 'Open', 'High', 'Low', 'Close', 'Volume', 'ABER_ZG_5_15',
         'ABER_SG_5_15', 'ABER_XG_5_15', 'ABER_ATR_5_15', 'ACCBL_20', 'ACCBM_20',
         'ACCBU_20', 'ATRr_14', 'BBL_5_2.0', 'BBM_5_2.0', 'BBU_5_2.0',
         'BBB_5_2.0', 'BBP_5_2.0', 'DCL_20_20', 'DCM_20_20', 'DCU_20_20',
         'HWM_1', 'HWU_1', 'HWL_1', 'KCLe_20_2', 'KCBe_20_2', 'KCUe_20_2',
         'MASSI_9_25', 'NATR_14', 'PDIST', 'RVI_14', 'THERMO_20_2_0.5',
         'THERMOma_20_2_0.5', 'THERMOl_20_2_0.5', 'THERMOs_20_2_0.5',
         'TRUERANGE_1', 'UI_14'],
        dtype='object')```