How to use the numexpr.expressions function in numexpr

names = {}
        for name in c.co_names:
            if name == "None":
                names[name] = None
            elif name == "True":
                names[name] = True
            elif name == "False":
                names[name] = False
            else:
                t = types.get(name, default_type)
                names[name] = expressions.VariableNode(name, type_to_kind[t])
        names.update(expressions.functions)
        # now build the expression
        ex = eval(c, names)
        if expressions.isConstant(ex):
            ex = expressions.ConstantNode(ex, expressions.getKind(ex))
        elif not isinstance(ex, expressions.ExpressionNode):
            raise TypeError("unsupported expression type: %s" % type(ex))
    finally:
        expressions._context.set_new_context(old_ctx)
    return ex

def stringToExpression(s, types, context):
    """Given a string, convert it to a tree of ExpressionNode's.
    """
    old_ctx = expressions._context.get_current_context()
    try:
        expressions._context.set_new_context(context)
        # first compile to a code object to determine the names
        if context.get('truediv', False):
            flags = __future__.division.compiler_flag
        else:
            flags = 0
        c = compile(s, '', 'eval', flags)
        # make VariableNode's for the names
        names = {}
        for name in c.co_names:
            if name == "None":
                names[name] = None
            elif name == "True":
                names[name] = True
            elif name == "False":
                names[name] = False
            else:

else:
            flags = 0
        c = compile(s, '', 'eval', flags)
        # make VariableNode's for the names
        names = {}
        for name in c.co_names:
            if name == "None":
                names[name] = None
            elif name == "True":
                names[name] = True
            elif name == "False":
                names[name] = False
            else:
                t = types.get(name, default_type)
                names[name] = expressions.VariableNode(name, type_to_kind[t])
        names.update(expressions.functions)
        # now build the expression
        ex = eval(c, names)
        if expressions.isConstant(ex):
            ex = expressions.ConstantNode(ex, expressions.getKind(ex))
        elif not isinstance(ex, expressions.ExpressionNode):
            raise TypeError("unsupported expression type: %s" % type(ex))
    finally:
        expressions._context.set_new_context(old_ctx)
    return ex

def stringToExpression(s, types, context):
    """Given a string, convert it to a tree of ExpressionNode's.
    """
    old_ctx = expressions._context.get_current_context()
    try:
        expressions._context.set_new_context(context)
        # first compile to a code object to determine the names
        if context.get('truediv', False):
            flags = __future__.division.compiler_flag
        else:
            flags = 0
        c = compile(s, '', 'eval', flags)
        # make VariableNode's for the names
        names = {}
        for name in c.co_names:
            if name == "None":
                names[name] = None
            elif name == "True":
                names[name] = True
            elif name == "False":

# Declare a double type that does not exist in Python space
double = numpy.double
if sys.version_info[0] < 3:
    int_ = int
    long_ = long
else:
    int_ = numpy.int32
    long_ = numpy.int64

typecode_to_kind = {'b': 'bool', 'i': 'int', 'l': 'long', 'f': 'float',
                    'd': 'double', 'c': 'complex', 's': 'bytes', 'n': 'none'}
kind_to_typecode = {'bool': 'b', 'int': 'i', 'long': 'l', 'float': 'f',
                    'double': 'd', 'complex': 'c', 'bytes': 's', 'none': 'n'}
type_to_typecode = {bool: 'b', int_: 'i', long_: 'l', float: 'f',
                    double: 'd', complex: 'c', bytes: 's'}
type_to_kind = expressions.type_to_kind
kind_to_type = expressions.kind_to_type
default_type = kind_to_type[expressions.default_kind]

# VML functions that are implemented in numexpr
vml_functions = [
    "div",  # interp_body.cpp
    "inv",  # interp_body.cpp
    "pow",  # interp_body.cpp
    # Keep the rest of this list in sync with the ones listed in functions.hpp
    "sqrt",
    "sin",
    "cos",
    "tan",
    "arcsin",
    "arccos",
    "arctan",

# make VariableNode's for the names
        names = {}
        for name in c.co_names:
            if name == "None":
                names[name] = None
            elif name == "True":
                names[name] = True
            elif name == "False":
                names[name] = False
            else:
                t = types.get(name, default_type)
                names[name] = expressions.VariableNode(name, type_to_kind[t])
        names.update(expressions.functions)
        # now build the expression
        ex = eval(c, names)
        if expressions.isConstant(ex):
            ex = expressions.ConstantNode(ex, expressions.getKind(ex))
        elif not isinstance(ex, expressions.ExpressionNode):
            raise TypeError("unsupported expression type: %s" % type(ex))
    finally:
        expressions._context.set_new_context(old_ctx)
    return ex

flags = __future__.division.compiler_flag
        else:
            flags = 0
        c = compile(s, '', 'eval', flags)
        # make VariableNode's for the names
        names = {}
        for name in c.co_names:
            if name == "None":
                names[name] = None
            elif name == "True":
                names[name] = True
            elif name == "False":
                names[name] = False
            else:
                t = types.get(name, default_type)
                names[name] = expressions.VariableNode(name, type_to_kind[t])
        names.update(expressions.functions)
        # now build the expression
        ex = eval(c, names)
        if expressions.isConstant(ex):
            ex = expressions.ConstantNode(ex, expressions.getKind(ex))
        elif not isinstance(ex, expressions.ExpressionNode):
            raise TypeError("unsupported expression type: %s" % type(ex))
    finally:
        expressions._context.set_new_context(old_ctx)
    return ex