code: public static Field create(Map<String, Field> v) {
      return new Field(Type.MAP, v);
    }
docs: Creates a <code>LIST</code> field. The keys of the Map must be of <code>String</code> type and the values must be
  of <code>Field</code> type, <code>NULL</code> values are not allowed as key or values.
  <p/>
  This method performs a deep copy of the given Map.
  
  @param v value.
  
  @return a <code>Map Field</code> with the given value.