def erase(string_letters: str, string_index: int) -> str:
    """Return the string_letters with the character at the string_index removed
    if the string_index is between range 0 and the last string_index.
    Otherwise return the original string_letters unchanged.

    >>> erase('assignment', 4)
    'assinment'
    >>> erase('assignment', 13)
    'assignment'

    """

    if string_index in range(0, len(string_letters)):
        return string_letters[:string_index] + string_letters[string_index + 1:]

    else:
        return string_letters