docs: def camelize(key):
      """Convert a python_style_variable_name to lowerCamelCase.
  
      Examples
      --------
      >>> camelize('variable_name')
      'variableName'
      >>> camelize('variableName')
      'variableName'
      """
      return ''.join(x.capitalize() if i > 0 else x
                     for i, x in enumerate(key.split('_')))