fixes error with types

metaflow/parameters.py

@@ -151,6 +151,7 @@ def __call__(self, deploy_time=False):
             return self._check_type(val, deploy_time)
 
     def _check_type(self, val, deploy_time):
+
         # it is easy to introduce a deploy-time function that accidentally
         # returns a value whose type is not compatible with what is defined
         # in Parameter. Let's catch those mistakes early here, instead of
@@ -166,7 +167,12 @@ def _check_type(self, val, deploy_time):
             % (self.parameter_name, self.field)
         )
 
-        if self.parameter_type in TYPES:
+        if isinstance(self.parameter_type, list):    
+            if not any(isinstance(val, x) for x in self.parameter_type):
+                msg += "Expected a %s." % TYPES[self.parameter_type]
+                raise ParameterFieldTypeMismatch(msg)
+            return str(val) if self.return_str else val
+        elif self.parameter_type in TYPES:
             if type(val) != self.parameter_type:
                 msg += "Expected a %s." % TYPES[self.parameter_type]
                 raise ParameterFieldTypeMismatch(msg)

metaflow/util.py

@@ -436,12 +436,16 @@ def to_pod(value):
         Value to convert to POD format. The value can be a string, number, list,
         dictionary, or a nested structure of these types.
     """
+    from metaflow.parameters import DeployTimeField, deploy_time_eval
+
     if isinstance(value, (str, int, float)):
         return value
     if isinstance(value, dict):
         return {to_pod(k): to_pod(v) for k, v in value.items()}
     if isinstance(value, (list, set, tuple)):
         return [to_pod(v) for v in value]
+    if isinstance(value, DeployTimeField):
+        return to_pod(deploy_time_eval(value))
     return str(value)