Update schema.py

Author: chalmerlowe

google/cloud/bigquery/schema.py

@@ -244,6 +244,22 @@ def __init__(
             self._properties["rangeElementType"] = {"type": range_element_type}
         if isinstance(range_element_type, FieldElementType):
             self._properties["rangeElementType"] = range_element_type.to_api_repr()
+        if isinstance(rounding_mode, RoundingMode):
+            self._properties["roundingMode"] = rounding_mode.name
+        if isinstance(rounding_mode, str):
+            self._properties["roundingMode"] = rounding_mode
+        if isinstance(foreign_type_definition, str):
+            self._properties["foreignTypeDefinition"] = foreign_type_definition
+
+        # The order of operations is important:
+        # If field_type is FOREIGN, then foreign_type_definition must be set.
+        if field_type != "FOREIGN":
+            self._properties["type"] = field_type
+        else:
+            if self._properties.get("foreignTypeDefinition") is None:
+                raise ValueError(
+                    "If the 'field_type' is 'FOREIGN', then 'foreign_type_definition' is required."
+                )            
         if fields:  # Don't set the property if it's not set.
             self._properties["fields"] = [field.to_api_repr() for field in fields]