code: def parse_conditional_derived_variable(self, node):
          
  
          if 'name' in node.lattrib:
              name = node.lattrib['name']
          elif 'exposure' in node.lattrib:
              name = node.lattrib['exposure']
          else:
              self.raise_error('<ConditionalDerivedVariable> must specify a name')
              
          if 'exposure' in node.lattrib:
              exposure = node.lattrib['exposure']
          else:
              exposure = None
              
          if 'dimension' in node.lattrib:
              dimension = node.lattrib['dimension']
          else:
              dimension = None
  
          conditional_derived_variable = ConditionalDerivedVariable(name, dimension, exposure)
          
          self.current_regime.add_conditional_derived_variable(conditional_derived_variable)
          
          self.current_conditional_derived_variable = conditional_derived_variable
          
          self.process_nested_tags(node)
docs: Parses <ConditionalDerivedVariable>
  
          @param node: Node containing the <ConditionalDerivedVariable> element
          @type node: xml.etree.Element
  
          @raise ParseError: Raised when no name or value is specified for the conditional derived variable.