code: def normalize_collaboration(collaboration):
      
      if not collaboration:
          return []
  
      collaboration = collaboration.strip()
      if collaboration.startswith('(') and collaboration.endswith(')'):
          collaboration = collaboration[1:-1]
  
      collaborations = _RE_AND.split(collaboration)
      collaborations = (_RE_COLLABORATION_LEADING.sub('', collab)
                        for collab in collaborations)
      collaborations = (_RE_COLLABORATION_TRAILING.sub('', collab)
                        for collab in collaborations)
  
      return [collab.strip() for collab in collaborations]
docs: Normalize collaboration string.
  
      Args:
          collaboration: a string containing collaboration(s) or None
  
      Returns:
          list: List of extracted and normalized collaborations
  
      Examples:
          >>> from inspire_schemas.utils import normalize_collaboration
          >>> normalize_collaboration('for the CMS and ATLAS Collaborations')
          ['CMS', 'ATLAS']