"""Parses and validates a string of triples into a list of tuples.

This function processes a string containing triples in one of two formats:
1. Newline-separated triples, e.g., '(e1, r1, e2)\n(e3, r2, e4)\n'.
2. Space-separated triples, e.g., '(e1, r1, e2) (e3, r2, e4)'.

The function performs several checks to ensure the triples are valid:
- Removes surrounding parentheses and single quotes.
- Splits each triple into its components (entity, relation, entity).
- Trims any leading or trailing whitespace from each component.
- Converts the components to lowercase if they end with a space.
- Validates that each triple is a tuple of exactly three non-empty strings.
- Excludes triples that contain 'note:' in the first component.

Args:
    triples_str (str): A string containing triples in one of the supported formats.

Returns:
    List[Tuple[str, str, str]]: A list of tuples, where each tuple represents a valid triple.
"""