input: Write a python function to create a directory, set it as the working directory, and copy files to it.
  assert create_and_copy("/usr/src/app") == "Directory created and files copied"
  assert create_and_copy("/tmp/newdir") == "Directory created and files copied"
output: import os
  import shutil
  
  def create_and_copy(dest_dir):
      try:
          os.makedirs(dest_dir, exist_ok=True)
          os.chdir(dest_dir)
          # Assuming files to copy are in the current working directory
          source_dir = os.getcwd()
          for file_name in os.listdir(source_dir):
              full_file_name = os.path.join(source_dir, file_name)
              if os.path.isfile(full_file_name):
                  shutil.copy(full_file_name, dest_dir)
          return "Directory created and files copied"
      except Exception as e:
          return str(e)