driver-core/src/main/com/mongodb/client/model/Filters.java
public static <TItem> Bson eq(final String fieldName, @Nullable final TItem value) {
        return new SimpleEncodingFilter<TItem>(fieldName, value);
    }
public static <TItem> Bson eq(final String fieldName, @Nullable final TItem value) {
        return new SimpleEncodingFilter<TItem>(fieldName, value);
    }
Creates a filter that matches all documents where the value of the field name equals the specified value. Note that this doesn't
actually generate a $eq operator, as the query language doesn't require it.

@param fieldName the field name
@param value     the value, which may be null
@param <TItem>   the value type
@return the filter
@mongodb.driver.manual reference/operator/query/eq $eq