# Get the value at `query`, a string of map keys and array indices
	#
	# The `query` is composed of map keys and array indices separated by "." (by default).
	# The separator can be set with `sep` to any string.
	#
	# Given the following JSON object parsed as a `JsonValue`.
	# ~~~
	# var jvalue = """
	# {
	#   "a": {
	#          "i": 123,
	#          "b": true
	#        },
	#   "b": ["zero", "one", "two"]
	# }""".to_json_value
	# ~~~
	#
	# Access a value in maps by its key, starting from the key in the root object.
	# ~~~
	# assert jvalue.get("a").is_map
	# assert jvalue.get("a.i").to_i == 123
	# assert jvalue.get("a.b").to_bool
	# ~~~
	#
	# Access an item in an array by its index.
	# ~~~
	# assert jvalue.get("b.1").to_s == "one"
	# ~~~
	#
	# Any error at any depth of a query is reported. The client should usually
	# check for errors before using the returned value.
	# ~~~
	# assert jvalue.get("a.b.c").to_error.to_s == "Value at `a.b` is not a map. Got a `map`"
	# assert jvalue.get("b.3").to_error.to_s == "Index `3` out of bounds at `b`"
	# ~~~
	#
	# Set `sep` to a custom string to access keys containing a dot.
	# ~~~
	# jvalue = """
	# {
	#   "a.b": { "i": 123 },
	#   "c/d": [ 456 ]
	# }""".to_json_value
	#
	# assert jvalue.get("a.b/i", sep="/").to_i == 123
	# assert jvalue.get("c/d:0", sep=":").to_i == 456
	# ~~~
	fun get(query: Text, sep: nullable Text): JsonValue
	do
		if is_error then return self

		sep = sep or else "."
		var keys = query.split(sep)
		var value = value
		for i in [0..keys.length[ do
			var key = keys[i]
			if value isa MapRead[String, nullable Object] then
				if value.has_key(key) then
					value = value[key]
				else
					var sub_query = sub_query_to_s(keys, i, sep)
					value = new JsonKeyError("Key `{key}` not found.",
							self, sub_query)
					break
				end
			else if value isa Sequence[nullable Object] then
				if key.is_int then
					var index = key.to_i
					if index < value.length then
						value = value[index]
					else
						var sub_query = sub_query_to_s(keys, i, sep)
						value = new JsonKeyError("Index `{key}` out of bounds at `{sub_query}`",
								self, sub_query)
						break
					end
				end
			else
				var sub_query = sub_query_to_s(keys, i, sep)
				value = new JsonKeyError("Value at `{sub_query}` is not a map. Got a `{json_type}`",
						self, sub_query)
				break
			end
		end
		return new JsonValue(value)
	end