# Example code:

# Import DTML from standard class and 
# get the HTML request and response objects.
from Products.PythonScripts.standard import DTML

request = container.REQUEST
RESPONSE =  request.RESPONSE

myString = '<dtml-var standard_html_header>'

# "Coerce" into a DTML-object
myDTML = DTML(myString)

# Return the rendered DTML by *calling* the DTML-object,
# in this case myDTML. context is the namepace - IMPORTANT
return myDTML(context, request, RESPONSE)

# RESPONSE can actually be ommited totally, since it is not used
# and defaults to None.  To restrict the namespace you can use 
# container instead, that way the DTML object will not aq vars
# outside the containing object/folder of this PythonScript