code: def annual_volatility(
      returns, period=DAILY, alpha=2.0, annualization=None, out=None
  ):
      """
      Determines the annual volatility of a strategy.
  
      Parameters
      ----------
      returns : pd.Series or np.ndarray
          Periodic returns of the strategy, noncumulative.
          - See full explanation in :func:`~empyrical.stats.cum_returns`.
      period : str, optional
          Defines the periodicity of the 'returns' data for purposes of
          annualizing. Value ignored if `annualization` parameter is specified.
          Defaults are::
  
              'monthly':12
              'weekly': 52
              'daily': 252
  
      alpha : float, optional
          Scaling relation (Levy stability exponent).
      annualization : int, optional
          Used to suppress default values available in `period` to convert
          returns into annual returns. Value should be the annual frequency of
          `returns`.
      out : array-like, optional
          Array to use as output buffer.
          If not passed, a new array will be created.
  
      Returns
      -------
      annual_volatility : float
      """
      allocated_output = out is None
      if allocated_output:
          out = np.empty(returns.shape[1:])
  
      returns_1d = returns.ndim == 1
  
      if len(returns) < 2:
          out[()] = np.nan
          if returns_1d:
              out = out.item()
          return out
  
      ann_factor = annualization_factor(period, annualization)
      nanstd(returns, ddof=1, axis=0, out=out)
      out = np.multiply(out, ann_factor ** (1.0 / alpha), out=out)
      if returns_1d:
          out = out.item()
      return out
  
imports: from __future__ import division
  import math
  import pandas
  import numpy
  from math import pow
  from scipy import stats, optimize
  from six import iteritems
  from sys import float_info
  from .utils import nanmean, nanstd, nanmin, up, down, roll, rolling_window
  from .periods import ANNUALIZATION_FACTORS, APPROX_BDAYS_PER_YEAR
  from .periods import DAILY, WEEKLY, MONTHLY, QUARTERLY, YEARLY
label_desc: Use image node_id 13 for calling a global function with example usage: annual_volatility(returns, period, alpha, annualization, out) and returns: out, out