text: """Implementation of Rule L012."""
  
  from sqlfluff.rules.L011 import Rule_L011
  from sqlfluff.core.rules.doc_decorators import document_configuration
  
  
  @document_configuration
  class Rule_L012(Rule_L011):
      """Implicit/explicit aliasing of columns.
  
      Aliasing of columns to follow preference
      (explicit using an ``AS`` clause is default).
  
      **Anti-pattern**
  
      In this example, the alias for column ``a`` is implicit.
  
      .. code-block:: sql
  
          SELECT
              a alias_col
          FROM foo
  
      **Best practice**
  
      Add ``AS`` to make it explicit.
  
      .. code-block:: sql
  
          SELECT
              a AS alias_col
          FROM foo
  
      """
  
      config_keywords = ["aliasing"]
  
      _target_elems = ("select_clause_element",)
  