input: Write a python function to parse command line arguments using argparse and return a dictionary with the victim's IP and MAC address, the gateway's IP and MAC address, and the network interface. 
  ```python
  assert set_configs(['-t', '192.168.1.2', '-g', '192.168.1.1', '-i', 'eth0']) == {
      'victim': {'ip': '192.168.1.2', 'mac': ip_to_mac('192.168.1.2')},
      'gateway': {'ip': '192.168.1.1', 'mac': ip_to_mac('192.168.1.1')},
      'iface': 'eth0'
  }
  assert set_configs(['-t', '10.0.0.5', '-g', '10.0.0.1', '-i', 'wlan0']) == {
      'victim': {'ip': '10.0.0.5', 'mac': ip_to_mac('10.0.0.5')},
      'gateway': {'ip': '10.0.0.1', 'mac': ip_to_mac('10.0.0.1')},
      'iface': 'wlan0'
  }
output: import argparse
  
  def ip_to_mac(ip):
      # This function should be implemented to convert an IP to a MAC address.
      # For this example, we'll just return a placeholder.
      return '00:00:00:00:00:00'
  
  def set_configs(args):
      parser = argparse.ArgumentParser(description='Parse network configurations.')
      parser.add_argument('-t', '--target', required=True, help='Victim IP address')
      parser.add_argument('-g', '--gateway', required=True, help='Gateway IP address')
      parser.add_argument('-i', '--iface', required=True, help='Network interface')
      
      parsed_args = parser.parse_args(args)
      
      return {
          'victim': {'ip': parsed_args.target, 'mac': ip_to_mac(parsed_args.target)},
          'gateway': {'ip': parsed_args.gateway, 'mac': ip_to_mac(parsed_args.gateway)},
          'iface': parsed_args.iface
      }