'"Given a bind value (i.e. a :class:`.BindParameter` instance),
return a SQL expression in its place.
This is typically a SQL function that wraps the existing bound
parameter within the statement.  It is used for special data types
that require literals being wrapped in some special database function
in order to coerce an application-level value into a database-specific
format.  It is the SQL analogue of the
:meth:`.TypeEngine.bind_processor` method.
The method is evaluated at statement compile time, as opposed
to statement construction time.
Note that this method, when implemented, should always return
the exact same structure, without any conditional logic, as it
may be used in an executemany() call against an arbitrary number
of bound parameter sets.
See also:
:ref:`types_sql_value_processing`'

def bind_expression(self, bindvalue):

    return None
