'Validate the input ``value`` and convert to expected attribute class.
The base method here does nothing, but subclasses can implement this
as needed.  The method should catch any internal exceptions and raise
ValueError with an informative message.
The method returns the validated input along with a boolean that
indicates whether the input value was actually converted.  If the input
value was already the correct type then the ``converted`` return value
should be ``False``.
Parameters
value : object
Input value to be converted.
Returns
output_value
The ``value`` converted to the correct type (or just ``value`` if
``converted`` is False)
converted : bool
True if the conversion was actually performed, False otherwise.
Raises
ValueError
If the input is not valid for this attribute.'

def convert_input(self, value):

    return (value, False)
