import datetime


def compact_mapping(obj):
    """Compact a dict/mapping by removing all None values."""

    return {k: v for k, v in obj.items() if v is not None}


def to_iso8601(dt):
    """Convert a datetime object to an
    `ISO 8601 <https://www.iso.org/iso-8601-date-and-time-format.html>`_ string.
    """

    return dt.strftime("%Y-%m-%dT%H:%M:%SZ")


def from_iso8601(s):
    """Convert an `ISO 8601 <https://www.iso.org/iso-8601-date-and-time-format.html>`_
    string to a datetime object.
    """

    return datetime.strptime(s, "%Y-%m-%dT%H:%M:%SZ")