input: Write a python function to get the positions of all pieces for a given player color in the ChessGame class.
  assert get_player_positions('white') == {"king": (7, 0), "queen": (7, 3), "bishop": (7, 2), "knight": (7, 1), "pawn": (6, 0)}
  assert get_player_positions('black') == {"king": (0, 0), "queen": (0, 3), "bishop": (0, 2), "knight": (0, 1), "pawn": (1, 0)}
  assert get_player_positions('red') == {}
output: class ChessGame:
      def __init__(self):
          self.board = {
              'white': {
                  'king': (7, 0),
                  'queen': (7, 3),
                  'bishop': (7, 2),
                  'knight': (7, 1),
                  'pawn': (6, 0)
              },
              'black': {
                  'king': (0, 0),
                  'queen': (0, 3),
                  'bishop': (0, 2),
                  'knight': (0, 1),
                  'pawn': (1, 0)
              }
          }
  
  def get_player_positions(player_color):
      return ChessGame().board.get(player_color, {})