input: Write a python function to activate a virtual environment using a given path.
  assert activate_virtualenv('venv/bin/activate') == 'source venv/bin/activate'
  assert activate_virtualenv('myenv/bin/activate') == 'source myenv/bin/activate'
  assert activate_virtualenv('env/bin/activate') == 'source env/bin/activate'
output: def activate_virtualenv(path):
      return f'source {path}'