old_contents: from math import *
  from typing import Callable
  
  
  # TODO: docs
  def parse(expr: str, args) -> Callable[[float, float, float], float]:
      return eval("lambda {}: {}".format(args, expr))
  
  
  def create_xs(a, b, n):
      h = (b - a) / n
      return [a + i * h for i in range(n + 1)]
  
new_contents: from math import *
  from typing import Callable, List
  
  
  def parse(expr: str, args: str) -> Callable[[float, float, float], float]:
      """
      Parse function from string
      :param expr: string, containing function expression. Just expression.
          It can contain fny variable from args and any math function (from Python's math module)
      :param args: list of variables in form of "x, y, z"
      :return: anonymous function -- lambda args: expr
      """
      return eval("lambda {}: {}".format(args, expr))
  
  
  def create_xs(a: float, b: float, n: int) -> List[float]:
      """
      Create mesh with step h = (b - a) / n and boundaries a and b.
      :param a: left boundary
      :param b: right boundary
      :param n: number of subintervals
      :return: list of floats
      """
      h = (b - a) / n
      return [a + i * h for i in range(n + 1)]
  
subject: add docs to utils