input: 
  from typing import List
  
  def analyze_executed_code(code: str) -> List[str]:
      """
      Analyze the given Python code to find all variable names that are used within the code.
      The function should return a list of these variable names.
  
      >>> analyze_executed_code("x = 10\ny = x + 5\nprint(y)")
      ['x', 'y']
      >>> analyze_executed_code("from math import sqrt\nz = sqrt(16)")
      ['sqrt', 'z']
      """
  
output:     import ast
  
      class VariableVisitor(ast.NodeVisitor):
          def __init__(self):
              self.variables = set()
  
          def visit_Name(self, node):
              self.variables.add(node.id)
              self.generic_visit(node)
  
      tree = ast.parse(code)
      visitor = VariableVisitor()
      visitor.visit(tree)
      return sorted(visitor.variables)