code: def zipline_root(environ=None):
      
      if environ is None:
          environ = os.environ
  
      root = environ.get('ZIPLINE_ROOT', None)
      if root is None:
          root = expanduser('~/.zipline')
  
      return root
docs: Get the root directory for all zipline-managed files.
  
      For testing purposes, this accepts a dictionary to interpret as the os
      environment.
  
      Parameters
      ----------
      environ : dict, optional
          A dict to interpret as the os environment.
  
      Returns
      -------
      root : string
          Path to the zipline root dir.