def activities_fields(query)
			defaults = {"only" => Object.const_get(name).fields.keys}
			query = defaults.deep_merge(query)
			only = ((Object.const_get(name).fields.keys & query["only"]) + ["created_at"])
			query["only"] = only
			return query
		end
def activities_fields(query)
			defaults = {"only" => Object.const_get(name).fields.keys}
			query = defaults.deep_merge(query)
			only = ((Object.const_get(name).fields.keys & query["only"]) + ["created_at"])
			query["only"] = only
			return query
		end
defaults for only.
if it is empty or nil, then it becomes all attributes
otherwise it becomes the intersect of all attributes and the ones specified in the only
created_at had to be added here, because otherwise it throws an error saying missing_attribute in the only. I think this has something to do with the fact that it is used in the query, so it will be included in the result.
@used_in: get_in_range
@param[query] : the provided query, expected to be of the structure:
{"only" => [array],,,other key value pairs}
@return[Hash] query : returns the query with the default values for the fields to be returned