(type = number) The required field count for all tuples in this space.
The arity can be changed with <code>box.space.<replaceable>space-name</replaceable>.arity = <replaceable>new-arity-value</replaceable></code>.
The field_count can be changed with <code>box.space.<replaceable>space-name</replaceable>.field_count = <replaceable>new-field-count-value</replaceable></code>.
The default value is 0, which means there is no required field count.