def colon_based_id_to_vep_id(colon_id):
    """Converts a colon-based identifier to VEP compatible one. Example: '15:7237571:C:T' → '15 7237571 . C T'"""
    id_fields = colon_id.split(':')
    assert len(id_fields) == 4, 'Invalid colon-based identifier supplied (should contain exactly 4 fields)'
    return '{} {} . {} {}'.format(*id_fields)