'Initializer.
Options include number of facets to discover, number of values for each
facet and the depth of the result to be considered for facet computation.
If you wish to discovering 5 facets with 10 values each in 6000 search
results, you can use a FacetOption object like this:
facet_option = FacetOptions(discover_facet_limit=5,
discover_facet_value_limit=10,
depth=6000)
Args:
discovery_limit: Number of facets to discover if facet discovery is
turned on. If None, discover facets will be disabled.
discovery_value_limit: Number of values to be discovered for each of
the top discovered facets.
depth: Number of documents in query results to evaluate to gather
facet information.
Raises:
TypeError: If an unknown attribute is passed.
ValueError: If any of the parameters have invalid values (e.g., a
negative depth).'

@datastore_rpc._positional(1)
def __init__(self, discovery_limit=10, discovery_value_limit=None, depth=None):

    self._discovery_limit = _CheckFacetDiscoveryLimit(discovery_limit)
    self._discovery_value_limit = _CheckFacetValueLimit(discovery_value_limit)
    self._depth = _CheckFacetDepth(depth)
