Filters the network data before the query takes place.
Return a non-null value to bypass WordPress' default network queries.
The expected return type from this filter depends on the value passed in the request query vars:
$this->query_vars['count']is set, the filter should return the network count as an integer.
'ids' === $this->query_vars['fields'], the filter should return an array of network IDs.
- Otherwise the filter should return an array of WP_Network objects.
Note that if the filter returns an array of network data, it will be assigned
networks property of the current WP_Network_Query instance.
Filtering functions that require pagination information are encouraged to set
max_num_pages properties of the WP_Network_Query object,
passed to the filter by reference. If WP_Network_Query does not perform a database
query, it will not have enough information to generate these values itself.