Attempt to convert indices into valid, positive indices.

    If we have negative indices, translate to positive here.
    If we have indices that are out-of-bounds, raise an IndexError.

    Parameters
    ----------
    indices : array-like
        The array of indices that we are to convert.
    n : int
        The number of elements in the array that we are indexing.

    Returns
    -------
    valid_indices : array-like
        An array-like of positive indices that correspond to the ones
        that were passed in initially to this function.

    Raises
    ------
    IndexError : one of the converted indices either exceeded the number
        of elements (specified by `n`) OR was still negative.

def maybe_convert_indices(indices, n):
    """
    Attempt to convert indices into valid, positive indices.

    If we have negative indices, translate to positive here.
    If we have indices that are out-of-bounds, raise an IndexError.

    Parameters
    ----------
    indices : array-like
        The array of indices that we are to convert.
    n : int
        The number of elements in the array that we are indexing.

    Returns
    -------
    valid_indices : array-like
        An array-like of positive indices that correspond to the ones
        that were passed in initially to this function.

    Raises
    ------
    IndexError : one of the converted indices either exceeded the number
        of elements (specified by `n`) OR was still negative.
    """

    if isinstance(indices, list):
        indices = np.array(indices)
        if len(indices) == 0:
            # If list is empty, np.array will return float and cause indexing
            # errors.
            return np.empty(0, dtype=np.intp)

    mask = indices < 0
    if mask.any():
        indices = indices.copy()
        indices[mask] += n

    mask = (indices >= n) | (indices < 0)
    if mask.any():
        raise IndexError("indices are out-of-bounds")
    return indices