"""Extracts predicates from a nested list structure.

This function recursively traverses a nested list structure to extract predicates. 
A predicate is defined as the first element of any non-nested list. If the input is 
a string, the function returns an empty list. The function assumes that the input 
is either a string or a list, and raises an AssertionError if the input is not a list.

Args:
    conds (Union[str, List]): The input structure to extract predicates from. 
                              Can be a string or a nested list.

Returns:
    List[str]: A list of predicates extracted from the nested list structure.

Raises:
    AssertionError: If the input is not a list (excluding the case where it is a string).

Examples:
    >>> get_predicates([['nested_predicate']])
    ['nested_predicate']
    >>> get_predicates([['pred1', 'pred2'], ['pred3']])
    ['pred1', 'pred3']
    >>> get_predicates([[['deeply_nested_predicate']]])
    ['deeply_nested_predicate']
    >>> get_predicates([['𘘨o']])
    ['𘘨o']
    >>> get_predicates([['0']])
    ['0']
"""