"""Splits a string into parts, respecting brackets and limiting to three parts.

This function processes a string by splitting it into parts based on commas, but it respects
bracketed content (i.e., content within '[' and ']') by not splitting within brackets. The
function ensures that the result contains at most three parts. If more than two commas are
encountered outside of brackets, the remaining content is treated as the third part.

Args:
    content (str): The string to be split. It may contain commas and bracketed content.

Returns:
    List[str]: A list of strings, each representing a part of the original string. The list
    will contain at most three elements. Each part is stripped of leading and trailing whitespace.

Examples:
    >>> _split_respecting_brackets('a,b,c')
    ['a', 'b', 'c']
    >>> _split_respecting_brackets('a,[b,c],d')
    ['a', '[b,c]', 'd']
    >>> _split_respecting_brackets('[a,b],c,d')
    ['[a,b]', 'c', 'd']
    >>> _split_respecting_brackets('a,b,[c,d]')
    ['a', 'b', '[c,d]']
    >>> _split_respecting_brackets('a,b,c,d')
    ['a', 'b', 'c,d']
"""
You should write code starting with:
from typing import List

def _split_respecting_brackets(content: str) -> List[str]:
    pass

