def merge_context(self, tag, metadata):
self.entities.append(tag)<EOL>for k in metadata.keys():<EOL><INDENT>if k not in self.metadata:<EOL><INDENT>self.metadata[k] = k<EOL><DEDENT><DEDENT>
merge into contextManagerFrame new entity and metadata.

Appends tag as new entity and adds keys in metadata to keys in
self.metadata.

Args:
    tag(str): entity to be added to self.entities
    metadata(object): metadata containes keys to be added to self.metadata