input: Write a function to evaluate a numerical expression given as a string and return the result. Ensure that the function handles basic arithmetic operations.
  assert eval_expr("3+5*2")==13
  assert eval_expr("(4+2)*3")==18
  assert eval_expr("10/2")==5
  assert eval_expr("7 - (2*3)")==1
  assert eval_expr("12")==12
output: def eval_expr(expression):
      return eval(expression)