code: def is_valid(arxiv_id):
      
      match = REGEX.match(arxiv_id)
      return  (match is not None) and (match.group(0) == arxiv_id)
docs: Check that a given arXiv ID is a valid one.
  
      :param arxiv_id: The arXiv ID to be checked.
      :returns: Boolean indicating whether the arXiv ID is valid or not.
  
      >>> is_valid('1506.06690')
      True
  
      >>> is_valid('1506.06690v1')
      True
  
      >>> is_valid('arXiv:1506.06690')
      True
  
      >>> is_valid('arXiv:1506.06690v1')
      True
  
      >>> is_valid('arxiv:1506.06690')
      True
  
      >>> is_valid('arxiv:1506.06690v1')
      True
  
      >>> is_valid('math.GT/0309136')
      True
  
      >>> is_valid('abcdf')
      False
  
      >>> is_valid('bar1506.06690foo')
      False
  
      >>> is_valid('mare.GG/0309136')
      False