This module contains class that represents a GDSII structure.
Bases: list
GDSII structure class. This class is derived for list and can contain one or more elements from gdsii.elements.
structure ::=  BGNSTR
               STRNAME
               [STRCLASS]
               {element}*
               ENDSTR
Initialize the structure. mod_time and acc_time are set to current UTC time by default.