(parser/state parser &opt key)
Returns a representation of the internal state of the parser. If a
key is passed, only that information about the state is returned.
Allowed keys are:
* :delimiters - Each byte in the string represents a nested data
structure. For example, if the parser state is '(["', then the
parser is in the middle of parsing a string inside of square
brackets inside parentheses. Can be used to augment a REPL prompt.
* :frames - Each table in the array represents a 'frame' in the
parser state. Frames contain information about the start of the
expression being parsed as well as the type of that expression and
some type-specific information.