The available columns for any given table are fetched from a system table called "sys_tablecolumns". A specific table name is provided in the WHERE criteria to restrict the table from which the column information is fetched:

import cdata.saparibasource as mod
conn = mod.connect("API=SupplierDataAPIWithPagination-V4;APIKey=wWVLn7WTAXrIRMAzZ6VnuEj7Ekot5jnU;Environment=SANDBOX;Realm=testRealm;AuthScheme=OAuthClient;InitiateOAuth=GETANDREFRESH;OAuthClientId=testClient;OAuthClientSecret=testClientSecret;")
cur = conn.cursor()
cmd = "SELECT * FROM sys_tablecolumns WHERE TableName = 'Vendors'"
cur.execute(cmd)
rs = cur.fetchall()
for row in rs:
	print(row)