class_docstr: Create a new Group that contains common members. All
  defined groups are stored in ``Group.groups``. Group
  names must be unique.
  
  Parameters
  ----------
  name : str
      Group name.
  space : alphapy.Space, optional
      Namespace for the given group.
  dynamic : bool, optional, default ``True``
      Flag for defining whether or not the group membership
      can change.
  members : set, optional
      The initial members of the group, especially if the
      new group is fixed, e.g., not ``dynamic``.
  
  Attributes
  ----------
  groups : dict
      Class variable for storing all known groups
  
  Examples
  --------
  
  >>> Group('tech')
code: def __str__(self):
      return self.name
  
file_path: AlphaPy/alphapy/group.py
imports: from alphapy.globals import USEP
  from alphapy.space import Space
  import logging
label_desc: Use image node_id 2 for calling the Group obj's underlying member method code with example usage: obj.__str__() and returns: self