Using Namespace

Hello everyone. Here I have my code using the eloquent. I am still confuse why I keep getting error in the line of "using namespace Eloquent::DataStructures;". Other info is that I am using the Arduino IDE of 1.8.15 version. Currently, I am doing my capstone project so fast reply would be appreciated

#include "eDataStructures.h"

#define MAX_NETWORKS 4

using namespace Eloquent::DataStructures;

double features[MAX_NETWORKS];
Array knownNetworks("");

void setup() {
Serial.begin(115200);
WiFi.mode(WIFI_STA);
WiFi.disconnect();

knownNetworks.push("SSID #0");
knownNetworks.push("SSID #1");
knownNetworks.push("SSID #2");
knownNetworks.push("SSID #3");

}

Here is the error message

Arduino: 1.8.15 (Windows 10), Board: "Generic ESP8266 Module, 80 MHz, Flash, Enabled, Disabled, All SSL ciphers (most compatible), 32KB cache + 32KB IRAM (balanced), Use pgm_read macros for IRAM/PROGMEM, dtr (aka nodemcu), 26 MHz, 40MHz, DOUT (compatible), 1MB (FS:64KB OTA:~470KB), 2, nonos-sdk 2.2.1+100 (190703), v2 Lower Memory, Disabled, None, Only Sketch, 115200"

sketch_sep14a:5:17: error: 'Eloquent' has not been declared

5 | using namespace Eloquent::DataStructures;

  |                 ^~~~~~~~

sketch_sep14a:5:27: error: 'DataStructures' is not a namespace-name

5 | using namespace Eloquent::DataStructures;

  |                           ^~~~~~~~~~~~~~

sketch_sep14a:8:1: error: 'Array' does not name a type

8 | Array knownNetworks("");

  | ^~~~~

D:\Arduino Data\sketch_sep14a\sketch_sep14a.ino: In function 'void setup()':

sketch_sep14a:12:5: error: 'WiFi' was not declared in this scope

12 | WiFi.mode(WIFI_STA);

  |     ^~~~

sketch_sep14a:12:15: error: 'WIFI_STA' was not declared in this scope

12 | WiFi.mode(WIFI_STA);

  |               ^~~~~~~~

sketch_sep14a:15:5: error: 'knownNetworks' was not declared in this scope

15 | knownNetworks.push("SSID #0");

  |     ^~~~~~~~~~~~~

exit status 1

'Eloquent' has not been declared

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