code: def find_crs(op, element):
      
      crss = [crs for crs in element.traverse(lambda x: x.crs, [_Element])
              if crs is not None]
      if not crss:
          return {}
      crs = crss[0]
      if any(crs != ocrs for ocrs in crss[1:]):
          raise ValueError('Cannot %s Elements in different '
                           'coordinate reference systems.'
                           % type(op).__name__)
      return {'crs': crs}
docs: Traverses the supplied object looking for coordinate reference
      systems (crs). If multiple clashing reference systems are found
      it will throw an error.