function getPMF( name ) {
	if ( !hasOwnProp( PMF, name ) ) {
		return new Error( format( 'invalid argument. Unsupported/unrecognized distribution name. Value: `%s`.', name ) );
	}
	return PMF[ name ];
}
Returns the probability mass function (PMF) corresponding to a provided distribution name.

@private
@param {string} name - distribution name
@returns {(Function|Error)} a probability mass function (PMF) or an error