class_docstr: Class to encapsulate the schema information for a heterogeneous graph.
  
  Typically this should be created from a StellarGraph object, using the
  :func:`~stellargraph.core.graph.create_graph_schema` method.
class_docstr_tok: ["Class","to","encapsulate","the","schema","information","for","a","heterogeneous","graph",".","Typically","this","should","be","created","from","a","StellarGraph","object",",","using","the",":","func",":","`","~stellargraph.core.graph.create_graph_schema","`","method","."]
docstr: Return edge type index from the type tuple
  
  Args:
      index: Tuple of (node1_type, edge_type, node2_type)
  
  Returns:
      Numerical edge type index
docstr_tok: ["Return","edge","type","index","from","the","type","tuple","Args",":","index",":","Tuple","of","(","node1_type",",","edge_type",",","node2_type",")","Returns",":","Numerical","edge","type","index"]
code: def edge_index(self, edge_type):
      """
      Return edge type index from the type tuple
  
      Args:
          index: Tuple of (node1_type, edge_type, node2_type)
  
      Returns:
          Numerical edge type index
      """
      if edge_type in self.edge_types:
          index = self.edge_types.index(edge_type)
  
      else:
          raise ValueError("Edge key '{}' not found.".format(edge_type))
  
      return index
  
file_path: stellargraph/stellargraph/core/schema.py
imports: import queue
  import warnings
  from collections.__init__ import namedtuple
  from ..core.utils import is_real_iterable
label_desc: Use image node_id 5 for calling the GraphSchema obj's underlying member method code with example usage: obj.edge_index(edge_type) and returns: index