Graph Pattern Matching Library

Assume that in an application, the user gives us a graph and we want to consider it as a pattern and find all occurrences of the pattern in a graph database (like neo4j). If we knew what the pattern is, we could write the pattern as a static query and run it against our database. However, now we do not know what the pattern is beforehand and receive it from the user in the form of a graph. How can we perform a pattern matching on the database based on the given graph (pattern)? Any library? Any APOC for neo4j?