parameters: (self)
return_statement: return typ
docstring: Return a copy of this type which has the :attr:`.should_evaluate_none`
          flag set to True.
  
          E.g.::
  
                  Table(
                      'some_table', metadata,
                      Column(
                          String(50).evaluates_none(),
                          nullable=True,
                          server_default='no value')
                  )
  
          The ORM uses this flag to indicate that a positive value of ``None``
          is passed to the column in an INSERT statement, rather than omitting
          the column from the INSERT statement which has the effect of firing
          off column-level defaults.   It also allows for types which have
          special behavior associated with the Python None value to indicate
          that the value doesn't necessarily translate into SQL NULL; a
          prime example of this is a JSON type which may wish to persist the
          JSON value ``'null'``.
  
          In all cases, the actual NULL SQL value can be always be
          persisted in any column by using
          the :obj:`~.expression.null` SQL construct in an INSERT statement
          or associated with an ORM-mapped attribute.
  
          .. note::
  
              The "evaluates none" flag does **not** apply to a value
              of ``None`` passed to :paramref:`.Column.default` or
              :paramref:`.Column.server_default`; in these cases, ``None``
              still means "no default".
  
          .. versionadded:: 1.1
  
          .. seealso::
  
              :ref:`session_forcing_null` - in the ORM documentation
  
              :paramref:`.postgresql.JSON.none_as_null` - PostgreSQL JSON
              interaction with this flag.
  
              :attr:`.TypeEngine.should_evaluate_none` - class-level flag
docstring_summary: Return a copy of this type which has the :attr:`.should_evaluate_none`
          flag set to True.
docstring_tokens: Return a copy of this type which has the : attr : . should_evaluate_none flag set to True .
function: def evaluates_none(self):
          """Return a copy of this type which has the :attr:`.should_evaluate_none`
          flag set to True.
  
          E.g.::
  
                  Table(
                      'some_table', metadata,
                      Column(
                          String(50).evaluates_none(),
                          nullable=True,
                          server_default='no value')
                  )
  
          The ORM uses this flag to indicate that a positive value of ``None``
          is passed to the column in an INSERT statement, rather than omitting
          the column from the INSERT statement which has the effect of firing
          off column-level defaults.   It also allows for types which have
          special behavior associated with the Python None value to indicate
          that the value doesn't necessarily translate into SQL NULL; a
          prime example of this is a JSON type which may wish to persist the
          JSON value ``'null'``.
  
          In all cases, the actual NULL SQL value can be always be
          persisted in any column by using
          the :obj:`~.expression.null` SQL construct in an INSERT statement
          or associated with an ORM-mapped attribute.
  
          .. note::
  
              The "evaluates none" flag does **not** apply to a value
              of ``None`` passed to :paramref:`.Column.default` or
              :paramref:`.Column.server_default`; in these cases, ``None``
              still means "no default".
  
          .. versionadded:: 1.1
  
          .. seealso::
  
              :ref:`session_forcing_null` - in the ORM documentation
  
              :paramref:`.postgresql.JSON.none_as_null` - PostgreSQL JSON
              interaction with this flag.
  
              :attr:`.TypeEngine.should_evaluate_none` - class-level flag
  
          """
          typ = self.copy()
          typ.should_evaluate_none = True
          return typ
function_tokens: def evaluates_none ( self ) : typ = self . copy ( ) typ . should_evaluate_none = True return typ